So, since this is a spoiler thread, I won't bother to hide my observations and theories.
We know that at the end of Clone Wars, Maul was running his Shadow Syndicate off Mandalore, though having just lost his brother Savage Opress to Sidious. We don't know exactly why Sidious left Maul alive, what his plans for Maul were, but some back-story we've been provided with indicates that Ashoka Tano was recruited by the Jedi to lead an assault on Mandalore, where Maul was defeated and driven off Mandalore, opening the door for the Empire to seize control of the planet. Anyway, the next time we saw Maul was at the end of Star Wars Rebels season 2, alone on Malachore. So somehow, he retained control of his Shadow Syndicate, or at least part of it, and renamed it "Crimson Dawn", and then would later have it destroyed or pulled out from underneath him, and get marooned on Malachore. I know this is a bit of a stretch, but perhaps this is supposed to tie in with the upcoming Kenobi movie?