Before the Misawa match on June 8th, 1990, Jumbo lost the Triple Crown to Terry Gordy three days earlier in a shock upset (Gordy lost the Triple Crown to Hansen that night in the semi-main). While the fans thought Jumbo was beating Misawa, after this lost they really though Jumbo was beating Misawa.
Misawa had just unmasked from being Tiger Mask II and going under his real name and was a big deal. That day, at the Budokon, the fans were going nuts for Misawa hours before bell time. Dave Meltzer was there and explained it as something he'd never seen before. Fans chanting MI-SA-WA in the ticket line and in the concourse. Still, no one though Misawa was going over.
Giant Baba was at the merch table and saw all this. So less than an hour before bell time, Baba sent a runner to Jumbo's dressing room to tell him. Misawa was going over. Jumbo was gobsmacked not because he didn't want to lose, but because this kind of request never happened. Baba was a long-term booker and rarely changed things on the fly and never right before the show.
Jumbo sent a runner back to Baba asking if the loss could be by count-out and Baba sent word back. No, by pinfall. So Jumbo, the biggest in-ring star of AJPW and three days before the Triple Crown Champion, crafted a masterful match where he would lose to the new rising star Misawa. Jumbo could have sandbagged the match and make Misawa look bad, but he didn't. Jumbo made Misawa a star in one night.
After Jumbo was pinned, the crowd lost their minds. Jumbo left the defeated old war horse while Kobashi and Kawada held Misawa on their shoulders in the ring. The new generation was here. According to Meltzer, out of the appx 15,000 people in the building (not quite a sellout but they literally sold out every Budokon show the rest of the decade afterward), maybe 12,000 people were crying, including Mrs Baba aka The Dragon Lady.
For every great match Jumbo had in the years before, putting over Mitsuhara Misawa in one match made All Japan Pro Wrestling the juggernaut it was under the Four Corners of Heaven (Taue, Kawada, Kobashi and Misawa) for the whole decade. When both men died (Jumbo in 2000 and Misawa in 2009), the first piece of wrestling footage the main news stations in Japan showed was their match from June 8, 1990. That says something about how the 30-somethings in Japan see that as a cultural moment. And that, IMO, is Jumbo biggest accomplishment.