Not only did people just assume Lexus was reliable, it actually was reliable. Of course, the original ES had the same exact drivetrain as the Camry V6, so not surprising. The flagship LS was a great car.
You are right about Lexus starting in 1989, it was Acura that started in 1986. Acura did quite well in the early years. But since 2009, when they went crazy with the "beak" grill, they lost a lot of market share, but are doing great with MDX and RDX SUVs. The RX (successor to the Legend) has kind of fallen off the cliff in sales.
These days, both Toyota and Lexus are testing the limits of "taste" with their grills, which IMO are almost as bad as old Acura beaks. At the same time, Acura has abandoned the beak, but is now sporting an Acura tuning fork logo that is way too big IMO. Personally, I think those stylists in Japan got a little to close to the Fukushima nuclear plant that blew up.