If you're a top player at one game but then that game stops doing tournaments, it is probably a hard decision whether to walk away or learn a new game.
Yes, a lot of motor skills might transfer over but a lot of knowledge is lost.
EG: League of Legends and DOTA 2 are similar games but different metas, different characters, some different mechanics entirely. It's enough of a gulf that you have to put in a lot of effort to cross over, especially at the high end.