Re: Were did Fender get the idea that they could make Humbuckers?
There are a bunch of things to unpack in OP's post:
Fender got the idea that they could make humbuckers a long time ago, with the legendary Seth Lover and his wide range pickups.
A full-size humbucker is not meant to be "Stratty". If Fender wanted a "Stratty" bridge pickup, they would have used a conventional Strat bridge pickup.
As for humbucker in a Strat not sounding good by itself, that I can believe. A big consideration in an HSS setup is how well the humbucker matches with the single coils. Either you go with a high output humbucker, so position 2 is like a conventional position 2, or you go with a low output humbucker that matches the singles in output. These balancing acts are hard to do well, IMO; I generally don't like HSS or HS configurations unless the S is a P90.
As for humbuckers in a Strat that do 60s or 70s rock, you may want to try the Pearly Gates Plus or normal Pearly Gates bridge pickup. The Plus version came stock with Texas Specials (which your Am. Special has, I believe) in the Lone Star Strat. If you have an Atomic humbucker in the bridge currently, that is pretty hot, and I can understand frustration with getting vintage sounds from that.
In general, though, I am a fan of Fender humbuckers. They've never struck me as super awesome, but they've always struck me as getting the job done. They wouldn't be my first choice for modern metal, but for everything up to hard rock and classic metal, pickups like the Blacktop and Atomic and Twin Head are pretty decent stock offerings.