90% of people don't understand karma because they have been sold a westernized version that has nothing to do with the original meaning.
Karma doesn't mean that if you do something bad, something bad is going to happen to you.
The principle of karma is that the world is a unique object we are all parts of. So if you harm someone or something in this world, you're basically hurting yourself because you're part of the same object.
I believe this to be very true. Life experiences and seeing the world through the lenses of cognitive intelligence led us to believe we are our own individuals separated from all the rest, and that our existence is limited to our body. So if there is no more body or if we die, there is no more us, there is no more you, there is no more me.
Except we don't pop up out of nowhere. In fact, before we develop in our mother's belly (what we consider the beginning of life), we live in two separated parts: the sperm cell containing half our genetic bagage and the egg present in the ovaries which has the other half. Literally, all of our being is contained in these two places. So me is not a single object or body. Before that, it's two things.
And even before that, before this sperm cell and this egg were produced, it's a bunch of atoms, molecules and energies floating around, ever transforming until they finally produce our being.
So when karma says we are a part indiscernable of the world we live in, it is technically true. Mankind is just the universe ever complexifying while it expands, to the point it is now able to look at itself. Which brings back to your conclusion:
From simple rules complexity can be formed.
That's what happening since the Big Bang. Bunch of atoms and energies projected everywhere and colliding ever after during their infinite course, creating shyt more and more complex.
And my heart aches realizing I'll never know why all that.