This means that nothing about free will is important in any decision making process, and thus free will is just a garbage concept that has no bearing or meaning in reality.

Even if there was such a thing as free will, it would be completely unimportant in decision making.

it is hard to imagine free will has nothing to do with why you don’t hold the tree morally responsible.

It doesn't, let's imagine free will separate from knowledge, reasoning, experience, etc. No amount of knowledge, reasoning, experience would prevent the tree from falling according to the laws of physics, that's why I don't hold the tree accountable. The tree has no knowledge, no reasoning, no experience, no morals, so, even if it could freely make the choice not to do it, because it doesn't have those things, it doesn't matter at all.