In this situation, Uber are complicit in the second sexual assault to at least some degree. (Perhaps they carried out a thorough investigation which presented nothing. Perhaps they did not carry out an investigation again). They are complicit in any further sexual assaults this driver carries out.
With regards to "Taking away a person's livelihood", that's precisely what a police investigation and CRB/DBS checks are for. The driver simply should not be allowed in such a position if they have a history of sexual assault. No-one is asking for the company to "act as judge and executioner" (in fact, in this case the company is doing exactly that except ruling not-guilty), merely to alert the appropriate authorities so that a legitimate investigation can be carried out according to the established judicial system.