Whalen got arrested in December 2018, so Trump only had two years to get him back...but your point is well taken.
It would be interesting to find out if Victor Bout for Paul Whalen was ever on the table during the Trump Admin.
To be honest, I’m glad that Trump didn’t try to release Whelan. He was discharged from the Marine Corps with a dishonorable discharge. I just found this out so I gave Trump a pass on trying to release him. There are a few others he could’ve tried I guess. But who knows if it was even doable.