Hyatt has a little over 600 hotels. That’s one-tenth the size of Marriott. There’s Marriott, Hilton, IHG, and Accor as players and there just aren’t chains in Hyatt’s peer group anymore.
They did try to buy Starwood themselves but their complex stock structure (two tiered stock giving outsized control to the Pritzker family) was a stopper and Marriott bested them. They tried to buy Kimpton but IHG was willing to pay far more.