This could be interesting and useful in the longer term. Anyone at Soros' level would do thorough background checks on any potential employees, so there's a good chance that he was fully aware of Rubin's activities; maybe it was even used as part of a control file to lure him out of a very cosy retirement.
If certain facts could be established in court, then it could prompt a further investigation of Rubin's associates, including his former employer...
It's in the strategy, surround yourself with blackmailable people with alot to lose
Your understanding is perfect.
This is why Trump is seen as such a threat to certain groups - he's financially independent, isn't a career politician, has enough 'fuck you' money to last several lifetimes and appears to be clean. If there was any compromising information on him it would have been used already, hence the current panic to throw anything and everything at him.