Couple things that come to mind:
1) SV software culture, kinda coming from Musk. This helps with battery pack management (important), electric motor control (important) and fancy car UI (less important perhaps but a "cool" factor. I think I count autopilot here)
2) Skin in the game. This is a bit meta, but some of the things they've done take some real guts and leadership. In their case it was do-or-die. Things like charger network, or getting the cars sold without dealerships, or building their own battery factory, or maybe the very idea of a production EV. I don't see this with incumbents - even if they have EV lines they could probably shut them down without much impact. Maybe this will not last long, I guess VW promised to switch to all electric new platforms? At that point they are kinda committed.
I think it partly is the car design. They were the first manufacturer trying to make a mainstream car which was designed from the ground up to take advantage of being a BEV (for example with batteries flat under the floor). Others always based their electric car upon an existing ICE design despite the ensuing compromises.
What I really have to give Tesla is: they have cars; they actually make them in factories they built; they built their own battery factory; they also invest into software side of things. And lastly they invested a ton into the charger network, which initially helped them get off the ground.
Other companies may have EVs but I feel they are not as invested / well matched to IC car manufacturer culture. But again, time and numbers will tell - who is actually making them, how many, and how well do they work.