They were responsible because their style of play developed into something the majority audience didn't want to watch. The rule change about being able to jump on serve was in place way before the 90s but the courts remained fast until the late 90s. So as I said the so serve and volleyers were responsible for their own demise. You mention the powerful racquets, funny how the majority audience wasn't bored with the baseliners equiped with powerful racquets but they were bored with the serve and volleyers using the same equipment. Hence serve and volleyers were responsible for their own demise, on both and all counts.
Majority of audience can relate better to the baseline tennis they actually play.
And some audiences who never plays just wants longer points whenever
they tune in for tennis all year long. Wimbledon increasingly estranged from
general public. Wimbledon finally succumbed to tennis outside Wimbledon.
That's the story.
When big servers were doiminating in 90's, Mary Carrillo argued new racquet
actually benefits baseliners more and predicted the game will eventually
evolve to baseline tennis. Simply because racquet manufacturers caters
more for general public who plays baseline tennis.
Tennis used to be a marketting tool for very very narrow and focused group of audiences.
To me, ATP seems to be attempting to make it as a marketing tool for wider
range of general public with series of changes and experiments like league formats.
IMHO, ATP has succeeded it brilliantly. Great rivalries at slams. I think we will see
more familiar players at all slams and all year long.