Like the article says and as applies to almost all failed startups / products, it can all be traced back to bad management.
I've been a heavy CS user for over a decade, I've been to events at their (now defunct I suppose) office in SF, I met their CEO at the time (one of many) and even did a walk around the block chatting strategy with their VP of Product at the time.
After building lifelong relationships through the platform, and comparing my experience as a user with management's side of the story, it was clear to me that they had very little understanding of their userbase.
Couchsurfers are broke. By definition. Meeting people is a huge value add, and the longer you stay on the platform, the more you gravitate toward the "community spirit" and less "saving money" side of things. But you are kidding yourself if you think that first time CS users are on the platform for any other reason than squeezing a few more days out of a thin backpacking budget.
Not only are they broke, but even the community often has an anti-money ethos. Just look at the outrage (as the article points out) when they switched to a B corporation. And it makes sense -- taking an inherently capitalist product (lodging) and building a community to make it free creates a very specific narrative.
Therefore, the expectation that CS users, especially first-time, will pay even a dollar on the service is DOA. They need to make money (exactly how much is up for debate), but this isn't the way to do it.
But that doesn't mean there aren't any other choices! CS Event sponsorships, cross-product integration (language learning, travel deals FFS), other corporate sponsorships, a more Airbnb-like private experience (maybe the community would hate that too, who knows), partnerships with local tourism authorities, discounted tour / event packages... None of these were even close to tried.
I'm not at all advocating that Couchsurfing should have become Tripadvisor, but to barely even consider a few alternatives to nickel and diming a bunch of broke backpackers just shows that CS was on its way out long before COVID-19...