This is strategically dumbest move he can make. Taylor Swift has been relatively quite for a while now regarding politics and now either she or her publicist is basically forced to respond to this. My best guess is Trump is trying to stir the pot to get any kind of attention but this isn't it.
Apple did remove Parler from the App Store in the past due to lack of moderation. It did not end well for Parler. I don't know how badly it has gotten over there on Twitter though. Is Twitter reaching the Parler level of toxicity yet?