This is the part that I think people are missing. Uber has a tight runway and burns a ton of cash every year. It needs focus, execution, and some more time (aka $$) to push this thing over the edge into profitability and IPO readiness. This means that Uber
may need some money in about a year if it isn't IPO ready by then. Someone here mentioned that at their current burn, they have less than a year of runway left.
So while Travis holds the majority of the voting power, he doesn't hold a ton of real-world cachet because of circumstance around the company. Uber is in a relatively fragile period in it's journey and no one at the top can afford to disagree right now so he has to mostly do what the big chunk of investors collectively tell him to do. The hope is that they can stay calm, run on autopilot without Travis for a bit and guide this cruise missile right through an IPO if everything goes according to plan. Since the investors effectively control the supply of additional capital, they are in a unique position of power here relative to Travis.
I think Uber's downfall is a bit exaggerated in the rest of these comments here. They'll go through some troubling times, but they just need to stay calm, and guide the ship. A lot of the pieces are already in place thanks to Travis, but Uber doesn't necessarily need him to oversee the next milestone the same way they needed him the past couple of years of insane growth.