While Siddhartha Gautama Buddha was still a prince who had never come in contact with any suffering before, he went outside the palace one day and had the great opportunity to witness the law of nature, of selfless impermanent changes of illness, old age and death, as well as the suffering of hunger and thirst, or survival instinct in all beings, and this experience had ignited the intense yearning for knowing the truth of existence or the yearning for liberation in him, which led to his renunciation from worldly life, learning from different teachers experiencing different paths, and found the middle path and attained enlightenment.
Knowing and respecting the law of nature, he never interfered with the law of nature, even though one of his teachings is about loving kindness, or non-violence, or non-killing. The non-interference towards the law of nature, observing all and everything arising, changing and passing away at their own cause, is indeed non-violence/loving kindness/compassion, which it's not easy for many sympathetic/empathetic minds to grasp.
Upon seeing the suffering of hunger and thirst, of the survival instinct in all beings, where the insect was being hunt and ate by a lizard, and then the lizard was being hunt and ate by a snake, and then the snake was being hunt and ate by a bird, and then the bird was being hunt and ate by a hunter, and then the hunter will eventually meet his own death and be eaten by worms and insects and animals, Siddhartha Gautama Buddha couldn't and didn't interfere with the law of nature.
Although he was deeply disturbed and grieving out of his nature of non-violence and loving kindness, he couldn't and didn't interfere towards nature. He didn't aspire to stop the hunter from hunting the bird, or stop the bird from hunting the snake, or stop the snake from hunting the lizard, or stop the lizard from hunting the insect, and so on.
When people who were in painful suffering came to him asking to be freed from sickness, to escape old age, and to bring back the dead, he didn't perform 'miracles' to remove all kinds of sickness, old age and death from anyone, for anyone. One can do one's best to stay away from sickness, to be cured from sickness, to stay young as much as possible, to save lives if possible, and to live as long as possible, but without attachment towards the fruit of action being what it is according to the law of nature, after doing one's best.
He let everyone to purify and discipline their own mind to see the truth of the existence of a selfless impermanent body and a selfless perceptive/cognitive mind governed by the law of nature, of cause and effect, of actions and the consequences of actions, or the restlessness of selfless impermanent changes of decaying, of selfless transitions of birth, old age, illness and death/disintegration, and be desireless and unattached towards the mind perception of a selfless impermanent life existence.
Decay/death/disintegration is not something terrible or negative.
It is the inevitable truth of everything - of living and non-living objects.
Regardless of being wise or unwise, kind or unkind, pleasant or unpleasant, selfish or unselfish, healthy or unhealthy, rich or poor, knowledgeable or non-knowledgeable, vegetarian or non-vegetarian, good or bad, right or wrong, agreeable or disagreeable, short lived or long lived, easy condition or difficult condition, all are subject to selfless impermanent changes of decaying, old age, illness and death.
He never mentioned or commenting about 'God existence', 'Soul or Spirit', 'Heaven and Hell'. He let everyone to purify and discipline their own minds, to quiet the modification of the mind, to inquire towards the truth of everything and attain self-realization towards the truth by oneself.
He didn't tell anyone what/how to think, what to believe and how to behave, or not. He let everyone to practice, or not, about the Noble Eightfold Path in order to purify, discipline and quiet the modification of the mind, to free the mind from ignorance, to know Thyself - the truth of Selflessness and Impermanence.
He didn't aspire to change the world to be something else that it is not.
He didn't aspire to stop the world from selfless impermanent changes governed by the law of nature, of cause and effect.
He didn't aspire to save the world from 'destruction' or 'extinction', or to free the world from 'painful suffering', 'evilness', 'wrongfulness'.
He didn't aspire to stop the teachings from changing into something else and disappearing from the world.
He didn't fight against anyone who act and react under the influence of ignorance or anything born out of ignorance.
He didn't desire or expect anyone or anything to change to be something different from what they are and are not. Everyone and everything will be changing as they are, governed by the law of nature, cause and effect.
He didn't judge or punish anyone or anything.
He wasn't a leader leading a group of followers. He wasn't a belief creator hoarding a group of believers. He was merely disseminating the Dhamma as it is, and let everyone whether to practice and liberate themselves from ignorance, or not.
His teachings and practice emphasize on - The Middle Path of respecting the nature of everything, or the truth of Impermanence and Selflessness, through Non-interference/Non-attachment/Desirelessness/Non-craving/Non-aversion towards the mind perception of names and forms (pleasurable enjoyment and painful suffering), and attaining Silence/Nibbana/Nirvana, or Annihilation of the modification of the mind.
He realized suffering isn't caused by the perceived names and forms being what they are, impermanently and selflessly changing. Suffering arise is due to ungratified desire deriving from attachment and desire of craving and aversion being generated towards the perceived names and forms, while attachment and desire of craving and aversion are the by-products of ignorance, being ignorant towards the truth of names and forms, of both the perceiver and the perceived.
Some people might mistaken Nibbana (in Pali) or Nirvana (in Sanskrit) - Void of the modification of the mind, as 'Heaven', one of the realms or states of mind that is still within the restless wheel of births and deaths governed by the law of cause and effect. The realm of 'Heaven' or 'State of supreme pleasurable enjoyment' is not ultimate liberation from the suffering of restless transition of realms, of the selfless cognitive mind perception of ceaseless impermanent changes of births and deaths (restless modification of the mind).
Inquire towards the truth of everything.