They are blocked from insider trading

I think this in the previous comment undervalue just how many more complicated ways there are for corruption to bubble.

Assume super strict rules. Consider this example to circumvent them: Senator-elect A makes an LLC and invest their money (with some friends) in it (before taking office)

They can’t even talk to the money manager. But the manager can see their actions, and the senator can know their ow investments and work in their favor.