Identity, culture, who makes these decisions?

Think about this:

"What and who determines company culture and who makes decisions in a larger company?"

I find myself sometimes confused about impossibilities and assumed ways that a company "works", or its culture and why it exists that way. The reason is that for many things inside that culture, there is not often a conscious decision by anyone backing it up, but rather some kind of "common assumption" that it simply is the way it is. This is detrimental for innovation and creates a certain culture of non-repudiation.

Could you say that the decision is made by anyone in a reasonably high position, which is then communicated and assumed or communicated as truth and reality by others?

To whom belongs (the culture of) the company in the end? Is it truly (fully) hierarchical? Are decisions consciously made?

Who do you talk to when you really feel like doing something, but do not carry out because you feel uncertain? Why do you feel uncertain? Who reflects actual decision authority? What would happen if this feeling is ignored and the idea is persisted anyway?