Game devs have embargoes where they provide early access to content creators and then set a date when they're allowed to talk about it. They publish as early as they allowed to but they're contractually obligated to not publish a moment sooner.
YouTube tends to show you streams or scripted videos about a certain game genre if you've watched even one video of that type before. So if you watch someone's Day Z video you're gonna see recommended videos like this.
Some creator discovered they get like 3 times the views if they have a conspicuous gun in the frame of the thumbnail. The only way to do that in a lot of extraction shooters is to reload the gun (or do the weapon inspect action if the game has that) and take a screenshot mid animation, so now they all do it.

Hence you get similar content and similar thumbnails at the same time.