You are right of course but Tesla initially was very bullish on insurance so why do we think they have stopped expanding the service?
Um. If memory serves, there was a period of time when insurers, mainly in California I think, were charging exorbitant premiums for any and all Teslas. It was pretty clear that they were doing this because (a) they could, (b) they were claiming that all the Teslas were root'n, toot'n sporty cars, and were thereby making a mint. And since it was most, if not all insurers in CA doing this, it was oligopoly city where the CA insurers were stiffing car owners.
As is kind of normal for Musk-owned companies that like to disrupt moribund industries (see: SpaceX. Or Tesla, for that matter), some bright light over at Tesla figured they could be an insurer themselves, make decent money, and put a stick in the eye to the likes of State Farm and all. And, once competition came back to the market, given that they had All The Driving Data, If They Wanted To Go That Route, might be able to do a better job than standard insurers with their silly dongles.
That was then, this is now. BEVs in general aren't that big an excitement that an insurer can get away with sticking it to the general public like they did to early adopters; further, insurers aren't blind, they can see Tesla and Tesla's premiums, so they're competing. As a guess, I wouldn't say that Tesla's losing money on the insurance business. But actuarial science doesn't need big casting machines or fancy factories in order to operate, just computers, so the barriers to entry are low. Low for Tesla - but low for everybody else, too. Actually competing on a more-or-less level playing field may be somewhat new for Tesla, so I'm not surprised if their expansion plans, which half-depended upon rapacious oligopolies balloons to stick a pin into, might be having a bit of a rough time (a) making a boatload of money and (b) expanding.