Here's my take;
1. Elon Musk. This is the source of it all, and not just Tesla. Also SpaceX (and the beneficial effects there), Tesla's Solar efforts, PowerWalls, The Boring Company, Hyperloop, etc. Nobody executes quite like Elon. SpaceX and their success has been mind-blowing lately. Getting Doug and Bob to the I.S.S. and back. Resupplying the I.S.S. Capturing boosters. Rockets landing on their pads?
All of this matters, because it's Elon as CEO. People want to be part of greatness, and all of this helps Tesla when it comes to the Elon and company's legacy, gravitas, and perceived momentum. The stellar history of TSLA stock and Tesla's valuation and projected value are all in the mix too. Tesla makes other companies look like they're standing still, though Nio and Lucid are promising. But as Elon has been known to say (paraphrased); prototypes are easy (in comparison to) production hell.
2. Range. Teslas have some of the best range, because EV is all they do and Elon Musk push hard to be the best. Battery Day proved that Tesla is still pushing the envelope. No company is going to catch Tesla anytime soon.
3. The Supercharging network. Nobody else can touch this. This is Tesla's 'Killer App' in my opinion.
4. Styling. Really, they have some of the best styling around. Their cars don't scream 'EV' so much as beautiful, timeless, flowing, minimalist, understated designs which hold up beautifully, from the first Roadster to the new.
5. EV Specialists. Tesla cars are all EVs, and nothing but EVs. They're not just making EVs to fulfill some government mandate, which is why Tesla is able to sell EV credits to companies that are making a token effort (Honda, I'm looking at you). Also, Honda needs to bring the 'E' to the States, small-car-fears be damned.
6. The userbase. The Tesla end-user is enthusiastic, so much so that Tesla doesn't feel any need to advertise.
7. Their cars are QUICK. More free-advertising. Gone are the days of range anxiety and slow econoboxes that look like they dropped in from Alpha Centauri....as long as you're in a Tesla.
8. Full Self Driving. This is going to be huge. Beta has been very promising.
9. OTA, or Over-The-Air updates. This is something anyone with a smart phone understands, and having new functionality from a simple software download is pretty great. I specifically avoided writing 'insanely great'.
10. Courage. Tesla has moxy, and doesn't seem to design by committee or focus group or by what is 'safe'. The Cybertruck is a prime example of this. Form follows function. That or my monitor is stuck on VRML graphics mode.