Why the Allies chose the Marianas over Rabaul

Why did the Allies not use Rabaul as a base and choose the Marianas instead?

The Marianas fit a more direct and supportable advance, while Rabaul could be bypassed and isolated rather than captured at high cost.

An island objective must be judged by the route into it and the route for keeping it supplied, as well as by the difficulty of capturing it. The Marianas lay on a more direct, protectable line from Midway and Wake and offered useful air and naval positions for the advance toward Japan. Rabaul could instead be isolated once other bases and sea lanes made it strategically unnecessary.