It started as a free speech Twitter alternative aimed at republicans. But along with republicans and free speech activists they've attracted right-leaning extremists that were banned from Twitter for a plethora of good reasons. As a result of those users being left unmoderated, Gab gained a certain reputation.

Gab's apps weren't accepted to either app store, they were booted by several hosting companies, had to switch domain registrar and their stripe account was suspended. Switch to a Mastodon fork is a recent development.