You can't give millions of dollars to politicians. There are laws, and yes, they're enforced.

It's not even "thousands". Those are actually just the individual employees making donations. You have to name your employer so that the election commission can make sure they aren't filtering money.

The power brokering happens in terms of trading favors. Often, trading votes. (And these days, "issue ads", which was the Supreme Court's big ole fuck-you to election finance laws.)