Not clear that it has. From FTA:
Uber’s global sales are still growing, with first-quarter revenues surging to $3.4bn, triple the levels of the previous year. However, its growth rate in the US is slowing and investors have become concerned after a period of crisis has left its top ranks in disarray.
In other words... the company is still growing massively, from a large base. It's just not growing as fast as it once did. As happens too often, the headline doesn't match the data.