The chain of causality that leads to thoughts and emotions in consciousness is completely determined by the structure and action potentials that propagate through our brain and nothing else, and this doesn’t leave room for some conscious agent in our brain also pulling levers and further modifying causality.
The differences between the lives of even identical twins in the same environment are a lot more than a flap of a butterfly's wings. They don't spend every second of their lives together, so their experiences will differ quite a bit.
A lot of our reasoning are applications of observations and best practices rules that we are sometimes not really aware of unless challenged by circumstances or outsiders.
This is to some degree necessary - the outside world is too complex to fully model inside our minds. The most important things that we can only build approximate models about are other people.
And based on what do you decide ? Probably your past experience, your knowledge, your education and your moral values. Which are all somehow environmental factors.
I'm largely swayed by the 'conscious experience.' Presumably neither of us believe that if you make a program to add 2+2, that some entity suddenly pops into existence and imagines itself to be adding 2+2 only to then zip out out of existence. Where we may differ is that I don't think that changes if we go from adding 2+2, to instead sequentially carrying out arbitrarily more simple instruction.
Yet here we are - 'passenger' or 'driver' in a body feeling as though we have complete control over our own actions. I tend to believe what lay before my eyes. And so in this case, I am obligated to reject this as being an emergent property of complexity, or as a facade. Which, in turn, obligates me to reject physicalism.
Perhaps it's that we all think in somewhat different ways, yet because our own mind is the only one that we will ever know - we simply posit that everybody else must think the same way, or at least quite similarly. For instance there's that weird datum that supposedly some huge percent of people don't have an inner monologue, at all. I find it extremely difficult to believe, but if it were true then it would certainly be much easier to understand how somebody else might not believe in free will.