I'm not sure that comparisons to the phone market, and the impact the iPhone had are apt. The EV market is hot, with a great deal of innovation happening already. Just this year we are seeing a ton of purpose-built EVs that provide real alternatives to Tesla. Automakers are rethinking the ergonomics of vehicles, now that they have different physical constraints than those powered by internal combustion engines.
Where Apple could have a real impact is in their ability to market and reshape people's thinking. Self-driving cars will be far safer and more efficient than what we have now, but it is going to be a big lift to get a critical mass of customers willing to use them. But Apple can call it iDrive or SuperMotion or whatever, and get people to value the idea.
I've no clue how quickly Apple can create a full-fledged car company. Maybe they only release a thousand vehicles in their first year. I don't really think that is the point for Apple. They have too much liquid cash. If they can turn that into another growing business, that's good for Apple in the long run. The Apple Car doesn't have to become ubiquitous overnight. It needs to just keep growing over time.
But I do think it is important to remember that it is unlikely that Apple has a killer feature here (like being first to market with a capacitive phone screen with an OS that made good use of it). Instead, they are stepping into a highly regulated, quickly advancing industry.