They acquired market power by killing them through predatory pricing, leaving incumbents unprofitable and forcing them to exit - while creating a steep barrier to entry for any new comers and strategically manipulating existing riders by offering high take rates initially and subsidising rides to create artificial demand and inflate market share - then once they kicked out the incumbents, they exercised their market power to raise prices and their % of the take rate of each transaction; leaving consumers and riders worse off.
We can talk all day about the nice UX blah blah. But the reality is, financially, they could not have succeeded without a very dubious and unethical approach.