Comment by vdupras

One explanation could be that, if Trump is a Russian asset, he'd be more effective at it if he wasn't obviously one. Seizing all tankers except russian ones might be too obvious.

Therefore, it might be worth it for Russia to lose a few tankers in order to keep one of their greatest assets.

All hypothetical of course. I'm sure Trump isn't a Russian asset. No way they can have kompromat on such a virtuous guy.