Potus has had way too much power ever since the Patriot Act (after 9/11).* It's barely a democracy anymore, and frankly it's a miracle that it took over 20 years before one took full advantage of what is "a broken system".

I'm sure there's more nuanced explanation in this specific case but ultimately it comes down to this: the US legal system is more holes than cheese.

Because they want to suck his cock.