I heard this in 1982 when i bought Apple stock.
Analogy warning!
The analogy to people who thought that "the incumbents" would crush Tesla would be people who thought that DEC, Unisys, etc. could make the transition to PCs.
IBM made the transition, but none of the other mainframe/minicomputer companies made it. They all declined.
Of the microcomputer companies which were operating before the IBM PC came out, Apple survived. The others didn't really -- they were taken out by the PC clone makers -- but they still did better than the mainframe/minicomputer companies.
At the time, any observer could have identified Apple, Commodore, and Tandy as the only ones which were plausibly likely to survive (and I did identify them as such); Tandy and Commodore actually made the transition to PC clones. Both were doing OK against the first wave of clones (Compaq etc.) but ended up being unable to compete on cost with PC's Limited (later Dell) and the other ultra-cheap clone makers; it took quite a while for the decline.
I don't see anything comparable to IBM entering the PC business; it would have to be a high-end company with massive brand reputation which could also produce in high volume and has an excellent quality reputation. Perhaps Audi or Porsche is the closest possibility, but neither has a good quality reputation. Also, IBM opened up their specs immediately (the IBM PC shipped with *extraordinarily complete* manuals) which gave them a huge advantage in third-party software and hardware developer sales over Apple/Commodore/Tandy -- I'm not seeing an equivalent in electric cars. (Though I will pay attention if it happens.)
There's no compatibility issue such as the one which tripped up Tandy and Commodore and Apple. Tandy also had a low-end reputation. I suppose it's possible that Tesla could go the way of Commodore, but Apple looks like a more likely analogy.