It’s nothing to do with [difficulties in using multiple platforms]. It’s to do with the massive backlash they got on Fedi for their CEO being all Trumpy and somewhat horrible right wing. So they’ve run away because they were made to feel unwelcome on account of us not letting their BS fly.
It’s to do with the massive backlash they got on Fedi
That makes no sense, considering the message in question was posted on Xitter, and the backlash they received was far worse and more public on Reddit, where they are directing their followers to go. It won't stop anyone from talking about them here.
The corporation doesn't have to stifle 100% of their criticism, they just need to disseminate enough of a counternarrative, with PR statements that are technically true enough, to overpower the criticism so that it no longer matters.
(Plus, based on your last comment, I know you already have a "they can moderate anything they feel like" response lined up, if they do start clamping down even harder where they can.)
The message was on Xitter from Andy Yen, but it was highlight on Mastodon by Jonah from Privacyguides.
The official Proton account also tried to defend Andy Yen on Mastodon (and later deleted it).