First marriages end 50% of the time [1], which doesn't seem that great. It's 67% for 2nd and 73% of 3rd. Given the large number that never remarry, the 2nd and 3rd order effects don't really add much to the overall rate.

>the rates have been improving

Maybe because record few people get married, and those that do, do so at record high ages [2].

[1] https://www.psychologytoday.com/us/blog/the-intelligent-divo...

[2] https://www.bgsu.edu/content/dam/BGSU/college-of-arts-and-sc...