User blog comment:Eobard95/Professor Stein dying - Ronnie returning?/@comment-1104107-20171001102356/@comment-1330227-20171002232703

They also killed off Laurel, Tommy, Eddie, and Snart.

Firestorm is special in that they can't really write off one character without the other so they have to kill them off. Stein can't simply decide to stay with his wife, or else Jax would have to go back to Central City and essentially disappear from all shows and it wouldn't make sense for them to introduce two new Firestorms to merge with Stein and Jax just for the one to disappear with Stein back to Central City.