The widespread nature of the problem is because small scale property crimes don't result in jail/prison sentences of any real length in CA anymore due to overcrowding in our jails/prisons. So, even when perpetrators are caught and prosecuted they won't spend hardly any time locked up. This very, very rarely happens anyway; police and prosecutors know they can't keep the perps in jail/prison for much time too, so why put in a lot of effort? Hence, it's viewed pretty much as a punishment-free crime and an easy way to make money for the criminally inclined or morally lax.
As for why that particular piece of glass and why so many Teslas? In general, breaking that small triangular pane of glass is less likely to trigger alarms on cars which have them connected to the glass. Which means more time for thieves to access the car without fear of being interrupted or discovered. Plus on the Teslas, which don't/didn't alarm for broken glass, you can reach your arm into the car through that area and easily reach the release to drop the rear bench seat-back. And, on Teslas, that release is something that can't be locked without resorting to aftermarket modifications/products which isn't very common. Upon which the thief can see whether there are potential valuables locked/hidden in the trunk which would otherwise be out of view. If there's something in the trunk, they will open the door to grab it or break more glass to be able to reach it. If not, they'll just walk away. Teslas in general, but Model 3s in particular, fit a bad vehicle demographic for this crime because 1) they either are high value cars or they are perceived as such and therefore more likely to contain valuable loot, 2) so many of them are new cars since the Model 3 has only really been out for a bit more than a year (again this is tied to likelihood of valuable loot, since the owner is well off enough to recently buy such an expensive car; but new cars of all types are more likely to be broken into than older models), 3) Teslas don't/didn't sound alarms when that piece of glass was broken and so became known within the smash-and-grab crews as an easy mark, 4) thieves can quickly gain access to the trunk and see if valuables are hidden.
I imagine it's such an issue in the Bay Area due to the relatively high density of Teslas in the area and "the word" went out to the Bay Area car thieves that it was easy on those pricey cars.
. Good luck with the insurance and hopefully no rain in the forecast.
