Every citizen of a democratic country, who is still inside Russia at this point, is a potential hostage and bargaining chip for the Russian government. There’s no independent press or judiciary in Russia and the Russian government has no morals and few scruples. If they need a hostage, they’ll take one.
Griner (a basket ball player convicted to 25y in prison for petty charges) was exchanged for Viktor Bout (the person on whom the movie Lord of War was based).
The Russian laws are also a minefield of post truths and petty rules, so it’s not hard to find some kind of charge against any individual. Basically everyone will be breaking the law in some way in Russia and the crooks in the Russian government can decide when and where to go after someone.