Twitter was also hemorrhaging money. The censorship had a chilling effect on the entire industry.
When have bans and restrictions hurt an established social company of some sort?
I see your point though. There are some people willing to take action and if one of those people is the richest in the world, those actions can be quite consequential. But that is one person, not society at large (either the power users of Twitter or the casual users of Twitter). Twitter didn't enter a commercial death spiral for banning Trump.
Tumblr.
Banning "creepy communities" and conspiracy subreddits on Reddit was about trying to make Reddit less of a haven for people who congregate to validate each other's potentially-dangerous ideas.
Banning Trump from Twitter was a straightforward matter of him serially breaking the rules.
Banning Substack links from Twitter is very clearly an attempt to harm a competitor, with no upside for users.
Trying to claim that the latter will be seen in the same light as the former two after some time has passed doesn't seem to follow logically.
This is the same by type. Twitter is hardly the only company engaged in this.
As Reddit banned all its creepy communities, people had a fit for a few days and made similar proclamations about how Voat would beat them as a result, and then life went on. It didn't destroy Reddit at all. Same with the crackdown on the conspiracy subreddits. Off they went to Voat. But Voat is gone and Reddit remains.
Twitter ended up banning Donald Trump and people discussed how it would be a watershed moment that would spawn this massive backlash and fuel Parler and Gab. But Twitter remains king. Parler and Gab haven't been something I have heard of in months.
All of these claims that a ban will cause significant damage to Twitter require people to fear that they will be next. Does Substack really have that kind of reach?