For those who don't know...
It's not just the money, the whole system Putin set up to stay in power relies on his trusted oligarchs and state cronies being able to operate their businesses with impunity, sucking money out of the Russian economy and into foreign assets.
If he can't guarantee their financial freedom and immunity from persecution, his hold on the country crumbles which is why the Magnistky Act and similar measures in other countries hurt him so badly.
Bill Browder testified to this recently before the US Senate.
If Mueller makes a compelling case that Trump is effectively a Russian agent placed in the highest office by clandestine interference, that by itself is an act of warfare. There are no good outcomes here.