"You must not have been worthy of his attention," Maul observes. When Sidious feels a threat is actually important, he goes out to take care of it himself. That's how Maul had known he actually had grown powerful enough to be considered one. If he hadn't, Sidious would have just sent an assassin to Mandalore to take care of him instead of showing up in person.

"Well, young Jedi, let us see how long you survive here before you end up perishing," Maul says. He'd made it four months in Deerington before he'd died the first time but not for lack of trying.