Actually it occurred right after platform laws were enacted that force manufacturers to run unnecessary crash tests if they make specific changes to a car (like a different transmission)
After platform laws went into effect only options that do not drive another $15m+ of testing will be offered , to a lesser extent emissions retest also plays a role but it’s easier to monetize across different platforms
Offering Boutique options like a manual transmission , different engine or drivetrain, minor body options used to be paid off with under 100 sales of said option a year, now that it’s 15 large the “option” has to fit in with other vehicles on the same platform to get enough volume to pay the testing .
Best recent example is the Prime solar roof, because of a 10lb object glued to the roof sheet metal it would drive a retest so Toyo pulled the option from the us market, the leafs solar option was legal because it was on a spoiler that is excempt from retest
Ignorant laws like platform and grey market law should be overturned and banned, then a manufacturer could cheaply offer low volume options, platform law is the #1 reason manual transmissions are gone,
the engineering and all other costs are sunk, just the $15 million testing that kills it