If Trump did nothing then why are people so scared of him winning the election?

because a leader that does nothing is an ineffectual leader. You want a leader that does something not nothing.

this also ignores the part where he tried to like, overthrow democracy, and ruin the government, but nobody likes to talk about that part.

How do you figure we don’t have an Oligarchy?

an oligarchy would be something like russia, The US as you said has multiple branches, the executive being the most front facing. You've got the judicial and legislative branches as well. The legislative branch (congress) is literally made up of hundreds of people. People that WE vote in.

black rock is also not a branch of the government, they're a private investment firm.