If you'd been listening to top 40 radio in 1990, you were witnessing the start of the decline of a format that lost 100+ stations between the late eighties and the early 2000s, partly due to vulgar rap music which chased away females, their kids, and baby-boomers who'd been listening to top 40 radio nonstop for 25+ years; some CHR/Pop powerhouses also evolved into Hot AC stations, while other top 40 stations were demolished by upstart rhythmic stations.
KPWR went from non-existent to #1 in less than a year here in LA in early 1987, deposing the humungous and then some KIIS-FM from the top of the ratings heap, and that stunned the entire industry from coast to coast.
KBBT did the exact same thing to KTFM in your fine city a few years later, IIRC.