What is Split timeline theory?

for a while now to fill the unexplained void left by sonic forces (because of course its sonic forces) fans came up with the theory called split timeline, what is it? and does it work? well lets find out. My Instagram and Twitter: https://www.instagram.com/dshaynie/?h...   / dshaynie   Sonic The Hedgehog is copyright Sega Music used: Title screen - Sonic Generations Sunset heights - Sonic Forces Egg Reverie - Sonic Mania Sonic Forces - Ghost Town - Turret 3471 Remix Final boss - Sonic mania Collision Chaos "G" mix - Sonic the Hedgehog CD Hard boiled heavies Boss - Sonic Mania Rooftop run Act 1 - Sonic generations Flying Battery Zone Act 1 - Sonic Mania Windy and Ripply (Emerald Coast) - Sonic Adventure