> If Trump were a Russian asset, what could he possibly do to advance their interests more than what he is already doing?

Rhetoric is a poor substitute for actual evidence.

Many moons ago, the fringe right used a similar argument to imply that Barack Obama was pro-ISIS. After his hasty withdrawal from Iraq, ISIS filled the power vacuum. Their "caliphate" grew for years and years, with no significant intervention from the US! At the time there wasn't a great answer to the question "If Obama were pro-ISIS, what could he possibly do to advance their interests more than he already has?". Yet (hopefully) we all know that this was simply bad faith, conspiratorial rhetoric. He was obviously not pro-ISIS, and there was no evidence whatsoever that he was. So how could people possibly have entertained such an idea? Easy--they already hated Barack Obama, so they were willing to give the conspiracy theory the benefit of the doubt.

Do yourself a favor and apply the old tried and true standard: extraordinary claims require extraordinary evidence. It'll save you a good deal of embarrassment.