They had to know what kind of scrutiny would be on those coins forever.
At the time of the theft, the coins are worth $100M+ and they can't touch them. Even worse, anything they do with them will be monitored, researched, dug into, and everything else from law enforcement, amateur detectives, and every major tech+crime group.
Fast forward to now and the coins are worth 50x that.. and now they try to move them? And all the keys are in cloud storage? But it had to be frustrating to be sitting on something so valuable without any way to use it. They had to be stressed and anxious about it.
A life of crime is stupid. A life of crime for something this high profile is far beyond stupid.
Could at least get a couple bucks from it, possibly.
Take 10 BTC and give them to 100 groups/people you don't like. Investigators make their lives miserable for a while.
For normal people, that'd be ridiculously expensive but since they didn't pay for the coins and have 100k+ more they can't use, it's "free."
They could easily point and say "dude I don't know who that was, here's those coins FBI".