It was a mistake to flee the US and a bigger mistake to never return.
He made it real easy for himself to be written off as a Russian asset.
If he stayed in the US he would've been thrown into a dark, black hole for all eternity to be tortured by the same types of sociopaths in the US gov't who committed atrocities like Abu Ghraib. I'll take being a Russian "asset" over the wrath of the US intelligence services any day of the week.
Had he stayed in the US whatever could he have done? The US are not known for their ability to accept wrongdoing.