One of the advantages Free Speech has is censorship is only worthwhile if deployed against ideas that have potential to attract people. One of my pet hobbies is arguing against socialism. I don't bother arguing against flat-earthism because nobody sane believes it. But socialism has some compelling points and people keep trying it.
That dynamic will help platforms like Parler. Whether or not the ideas are good ones, the people there going to be people who were pushed off Twitter because they had compelling or persuasive ideas.
Can't meet bad ideas by silencing people. It doesn't work, people just get the impression that the ideas have power.