Quite often the reasons for the popularity of such channels are quite obvious. It's no secret that public taste is horrendous- everyone likes Marvel movies. And the second reason that such YouTube content makers approach their YouTube careers quite rationally unlike the guys who make something perfect with heart and passion. The lasts usually don't use the simplest Youtube SEO tools like https://backlinkvalidator.com/tools/youtube_tags_tools.php
I get this chick's page recommended to me all the time, probably because I watch gaming channels...her commentary on everything is just so basic, and she's only getting a lot of views because she's sort of attractive.
I watch a lot of time-wasting content, but seeing a massive slab of ice melted through by a thousand-degree iron ball is really really cool. This is just completely empty and worthless.
While you can't tell if a video is going to be good based on the thumbnail alone, you can almost certainly tell if a video is bad based on the thumbnail.
If the thumbnail consists of some person making an obviously exaggerated expression, or if there are emojis placed all over the place, there's a 99% chance the video is going to be absolute trash.
Luckily these types of videos are found mostly in pop-culture videos about video games, movies, music, etc. which I don't watch so this isn't a problem for me.
But sometimes there are even tutorial and review channels that use clickbait thumbnails (mostly the larger channels...wonder how they got so large...) so I will sometimes use the GUI if I am looking for a video to watch.