Feels fairly simple. A decent chunk of people always disliked SPAs, due to their very obvious disadvantages. Another chunk of people always liked them, either due to novelty or to their, again, fairly obvious advantages.

Depending on who you talk to or what online forums you frequent, you may have had an impression that the first group was far smaller (or larger) than the last group. Due to changes in the media you consume, or changes to the culture of various online forums, it may seem to you like the first group is now larger (or smaller!) than the second instead.

On the margin I suppose a few people who liked SPAs due to the novelty may have got bored with them, but most people, I think, have had pretty static views about SPAs, because the pros and cons are pretty obvious.

Yeah, okay, some prominent engineer tweeted something bad about SPAs last month and it went semi-viral, but prominent engineers have been tweeting and writing bad things about SPAs for the entire existence of SPAs. And more than a few of those have gone pretty viral.

Better question might be "How come I saw this tweet on my feed, but didn't notice all the earlier ones?", but I don't think that's super interesting.