Idk much about how they decide ban periods and all that shit, or how big an impact elo boosting has on the game vs toxicity, but I'll just give my 2 cents. I read a few months back about how that Commando Yi guy got banned for elo boosting his friend, and one of the rioters said after he boosted his friend to silver 1 or gold 5 (whichever it was) he lost several games in a row and got demoted all the way back to silver 4. That rioter implied the main problem was how many people he affected in his loss streak because he was boosted into a higher elo and therefore caused many of the players that earned their way there undeserved losses. So if XWX boosted several people and some of them had the same results as Commando Yi's friend, the impact might be much harsher. In the case of a toxic player, he was probably still trying to win games, but was being aggressive vocally. In that case, you mute him, report him, and he still probably had less of a negative impact on the game.
Now the fact that Forg1ven had only a 4-game ban kinda disturbs me, since he already had a previous history of toxicity, I feel the punishment should've been higher.