The Davis study doesn't make any of the big claims that are getting attention here. Being academic and from a good department, it is much more measured:

"Net vehicle miles traveled (VMT) changes are unknown."

"While this data provides initial insights into the travel behavior changes associated with ridehailing, it is still limited in that it does not provide a complete picture of individual travelers’ trip generating activities, the modes they used before ride-hailing services, and the potentially new patterns of behavior that have since emerged."

Meanwhile, here is coverage of this study: "Lyft, Uber increase traffic 180 percent in major cities, says report" https://sf.curbed.com/2018/7/27/17622178/uber-lyft-cause-tra...