Add content and do slight update to all pages. Resubmit. Add new content as a silo. That should help as you investigate what is going on. Not sure if using affiliate like Amazon or reviews, but those took a hit.
1001 things that could be wrong. Hard to say what the cause could be, maybe quality of content, high % affiliate posts, or maybe the intent is wrong. But going from 20 clicks to zero clicks is difficult to analyze as it could just be 1 post that has lost rankings.
Luckily, I've only had 2 websites that have been affected by core updates over the last 15 years.
For both of the affected websites, it took around 18 months for those websites to recover SERP positions. That was after re-creating them from the ground up - new code, content, links, JS... everything!
It took me a huge amount of dedication, hard work, and soul-searching, but it was worth it: those two websites are now my highest performing sites.