The focus shifted when hip-hop started blew up in the mainstream.
Your video evidence is
Malibu's Most Wanted @Mandarin Duck , when white people saw a place for themselves in hip-hop they started focusing on what rappers as a proxy to black culture were focusing on, ass was part of the package. It was gradual, you said so:
But looking at it now, I wouldn't consider that a lot of ass
They wasn't paradin' ass like that and they still not if you payin' attention. That's black culture, the standard of ass changed 'cause hip-hop made it acceptable. JLo came at the right time when Diddy's profile was a sign of hip-hop hittin' the mainstream at the turn of the century... but that's hip-hop influence. If Diddy was a R&B record exec dancin' in the videos she woulda never been in the conversation. She in the talks 'cause of hip-hop, she the crossover bird that made somethin' that was always a fixture in the community acceptable for
others, other women could now see themselves in hip-hop.
No coincidence low-rise jeans became popular in the early 00s in hip-hop. Gotta give Sir Mix-a-Lot credit way back in '92,
Baby Got Back was co-produced by Rick Rubin... in '92. See?
Before JLo...? Probably Adina Howard, but I would putta stronger wager on Lil Kim and maybe even Foxy Brown that random video vixens and chicks in booty magazines.