They can't, its a massive misunderstanding.
It's just a fine, and suspended 1 match ban it's worded weird, it means he is like in a probation for next year. If he does any thing similar within that period it's immediate 1 match ban.
Demiral shouldn't been banned until they sure, let alone 2 games. Turks says its just a symbol for national animal Wolves. And UEFA says its a far right extremist/fascist symbol.
Maybe Demiral could just said its inside joke with friends in the stand like Jude did and it would been a fine.
Either way, Jude shouldn't be banned either, even if his seemingly directed at opponents. Diego Simeone and Cristiano Ronaldo done similar gestures in past lol, with no bans, but fines.
The iffy part is banning Demiral 2 games, basically their best defender, for a hand gesture they not even 100% sure what he meant by. If confirmed it's political, yeah ban him, but if there's ambiguous nature to it, then it's more tricky.