Guitarist and a hobby luthier here.
So to give some quick history, big traditional brands like Gibson and Fender entered a slump back in the mid 60s. The companies were bought out by Norlin and CBS at the height of the electric guitar popularity, and things took a turn for the worse when all the cost-cutting measures started becoming noticeable. Hence why 50s and 60s guitars from those brands cost a fortune today.
This decrease in quality ushered in an era of Japanese manufacturers producing high-quality copies of both Gibson and Fender guitars. They straight up copies the guitars, but often made them better than those available at the time (mid 70s, when both Gibson and Fender were at the lowest point).
Gibson acted fast, and filed lawsuits against those brands. Some big household brands today, like Ibanez, obliged and went onto making their own designs which became wildly popular. Other brands, like Tokai, Greco, Fernandes, and many others continued to make their Gibson and Fender copies for the Japanese market. AFAIK, those guitars could not be sold in the US due to the lawsuits.
Eventually both Gibson and Fender came out of the slump in the early 80s. By now, there was a whole cottage industry of boutique / custom guitar makers in the US making high-end stratocaster and telecaster (S- and T-style) type guitars - these brands were making guitars for the discerning customer, in a time where Fender didn't have any custom shop option. Schecter was one of the big emerging brands back then, making high-quality guitars for players like Mark Knopfler. You then got brands like Tom Anderson, Zion, Pensa-Suhr, and others. In the late 80s they all landed on using their own headstock shapes and slightly different S- and T-style bodies. Probably to avoid paying licensing fees to Fender.
Traditionally, the only thing that was completely off-limits, used to be the headstock. If you made a Fender style headstock, or open-book Gibson style headstock, you'd hear from their lawyers - that's just how it always was.
Brands like Charvel, which made their name in the early 80s by using Stratocaster headstocks, did not produce any US made guitars with such a headstock until they were acquired by Fender FMIC 20 years later. Even smaller boutique builders had a thriving industry making Charvel "Strathead" replicas back in the 90s / early 00s. But the bodies they used were very clearly S- and T- style bodies. Again, Fender didn't seem to bother. Fender tried to register (in the US) their most common bodies in 2009, but that was rejected.
So the long short has been that for all these years, pretty much since the 60s and 70s, the bodies have been more or less "public domain", in the sense the Fender didn't go after anyone that made those bodies. And again in 2009, they failed to trademark the body designs.
In the 2000s/2010s guitar production in China really took off, and became the leading producer of cheap guitars. Prior to that, it used to be Indonesia. Prior to that, Korea. Prior to that, Taiwan. Prior to that, Japan.
The sheer production capacity, and price, made it possible for pretty much any in-store brand or budget brand to pump out S- and T-style guitars. For every US made Fender, there are probably 100 Chinese made for brands like Harley Benton. And then you also have the straight up replicas sold on AliExpress, Temu, and what have you. These also use to Fender headstock.
All this has lead to where we are now. Fender sued some Chinese company, won by no-show in Germany, and are now trying to go after all brands that use the S- and T-style *body shape*.
Why is this huge? Well, for one the body shape is by now so generic, it would be like Ford suddenly suing all car manufacturers in the world because they are creating cars with a generic sedan or station wagon body design. If we continue with the car analogy, think of the headstock as a very distinctive thing on a car - like the logo and front grill. Of course, some bodies are unique - like flying V, Explorer, Les Paul.
But for the lack of a better explanation, history just made the Fender Strat and Tele styles generic. Probably due to the lack of enforcement from Fender, and patents expiring in the 60s/70s for those things.