I know someone who owns several and is quite wealthy. He started out owning a small, shitty car wash and he gradually built/acquired more and upgraded them. You succeed in business the same way you succeed in any other aspect of life, you either get lucky or you work hard or some combination. In his case it was mostly hard work over at least a decade.

The fixation so many people in the comments have on starting a carwash is why most businesses fail. The right approach is to figure out what you're likely to succeed at and start that business, not to pick one because it has a high valuation and copy it (this is how must tech entrepreneurs work). Maybe the carwash market is saturated, some other market isn't and someone will make a bunch of money filling that gap.