Board Thread:Speculation, Theories, and Rumors/@comment-4892653-20170317204901/@comment-477304-20170321151744

If you think about it, Eggman's usually accomplished most of his scheme by the time Sonic shows up; he'd already built the Death Egg in Sonic 2, released Chaos in Sonic Adventure, discovered Gerald's work in Adventure 2, built an air fleet in Heroes, split the world into pieces twice in Unleashed and Advance 3, enslaved an planet and it's indigenous lifeform, and various other achievements before the game even starts.

Eggman could simply send Sonic on a wild goose chase, pretending to have a different scheme in motion, waiting for the right moment to unleash his true plan and Sonic would be unable to stop it.