BJJ took a strong hold for a long time. The stand up game came back once fighters became more successful in escaping the grappling submission attempt. They do a much better job with staying off the ground.
It was BJJ domination for a little while but then the Wrestlers started to take the reign. Maurice Smith was the one who turned it around for the Strikers. But Wrestling & BJJ still held it, just not as dominant. Then the Senate investigations, leading to many more rules such as time limits => resetting to standup, which the Gracies greatly protested.
But IMO, it was Dana White's edict/nudge that he wanted to see more exciting fights; translated to, more standup striking and less "human blankets". So if you were a Human Blanket stylist, ie. Demian Maia, you'd get less fights and less $$$. Many of the BJJ & Wrestlers adjusted and trained more striking, ie. Colby Covington, who was super boring but now, a lot of striking and antics.
I think we will see San shou crossover occur with the increased striking that we see. At least I hope we see it. I'm with you about Cung Le. Bad timing as he entered at the end of his fighting career. It appeared to be more of."yeah I can do this" and less "I'm going to dominate MMA" He didn't have much of a challenge and MMA was that next level for him. He did it and was satisfied.
I'm a big fan of Cung Le, but I thought the last few of his fights, there were backroom deals to not take him down to keep it exciting. One of the dudes he beat was a big time wrestler, yet didn't try to TD him once. It's been a long time, but I recall it was a White dude with platinum dyed hair.
Also, if you look at Cung Le's training, his main achievements in high school was Wrestling. Before that, he was a little kid in a strip mall TKD school. He really didn't train too much Kung-Fu that I could find. I see him training more Muay Thai than KF, esp. with Arjan Chai. He fought in Sanda/Sanshou because in NorCal, there's a ton of Asians, esp. Viets and Kung-Fu is big among Viets, which meant more Sanda type, big tournaments. So to become famous, a fighter would fight Sanda at a stadium, rather than TKD or Karate at a high school for a plastic trophy. Muay Thai wasn't even popular yet, back then.