crossfit made the gym (and free weights) cool
crossfit became popular as a side effect of "bootcamp" style workouts in the 2000s-2010s, like the Spartan Run, Tough Mudder, Rucking, etc.
mark rippetoe, creator of Starting Strength, was heavily involved in crossfit. between that and him franchising his Starting Strength practice, powerlifting became more widely practiced. once Instagram started building lifestyle brands around this (gymshark, alphalete, nobull, darcsport, etc.), it was a lock.
This stuff comes in waves and every generation thinks that it's unique. Adidas was originally a pro fitness brand like Gymshark is now. Gymshark will become athleisure just like Adidas, it's just a matter of time.
Crossfit is just the name for HIIT training that's pumped as a new branded workout. Note that already it's now Hyrox. It will be something else in a few years.