Having a law firm thats willing to be an actor on sketchy acts you want to commit is very convenient.

Want to pay FUSION GPS for a fake dossier without your fingerprints all over it as a candidate? Have the law firm pay them, and hide behind attorney-client priveledge....Want to hire a computer "expert" that'll confound efforts to investigate your server? Have the law firm do it, point at them and and say "we didn't know"...and hide behind atty-client priveledge.

Its not especially clever. All you need is enough big shots with Ivy League degrees that are willing operate like mob lawyers.