Trump says he WILL fire Mueller if he starts to look into Trump’s finances. And, now the cat’s out of the bag. Once Mueller starts looking at the finances, we’ll find clear connections, albeit probably legal business ones, with various Russian entities. That certainly makes the case for collusion stronger if any of those entities were also trying to garner influence with Trump.
Frankly, if Trump fires Mueller Trump’s finished. That’s obstructing justice, that’s an impeachable offense.