Twitter is just a conduit for news, in the same way paper is for print media or pipes are for sewage. Trump isn't being silenced, he has/had other options, including acting responsibly.
I'm surprised at your stance. He, and his allies and followers, have been spreading falsities about people for their own benefit. Taking on such a group in court for libel/slander is going to be costly, potentially fateful and moreover, gives publicity to their poison, even if you win. Trump knows this.
If you think about social media as a newstand, with each account its own publication, that's more accurate. After all, you wouldn't expect W H Smith to sell QAnon Weekly*.
*Any similarity to actual publication is purely coincidental.