Before we go into how clickbait works, let's define it. I like the Merriam-Webster definition better than Wikipedia's version. M-W defines clickbait as: "Something (such as a headline) designed to make readers want to click on a hyperlink especially when the link leads to content of dubious value or interest."
Sometimes clickbait is more like bait and switch. That is, we read a catchy headline or link, click it, only to find ourselves enveloped in an ad. The majority of clickbait is of the "dubious value" variety. There is content when we click on the link, but it is heavily wrapped in advertisements. Thus, the article or video is in actuality a lure that exposes us to the ad, which is the true purpose of the content. When enough people are exposed to the ads, there will be a percentage of us who become buyers of the products being marketed. Again, we know this clickbait model works well enough because, if it didn't, it wouldn't exist. It's a product of Darwinian capitalism.
Lots of vivid graphics
Lots of cutesy/busy graphics
Colored frames around the thumbnail to catch your eye
Clickbait titles - something presented as provocative which turns out to be very underwhelming
Inflammatory language in descriptions
Intense, up close pictures
If you click, they make money
BBC News: do you see any of the "techniques" used in their thumbnails?
PBS News: do you see any of the "techniques" used in their thumbnails?
Fox News: do you see any of the "techniques" used in their thumbnails?
CNN: do you see any of the "techniques" used in their thumbnails?
These creators are not desperately trying to attract viewers. MaCenna has established herself and doesn't have to pander for clicks.
Martin is happy just as he is. He's not trying to become an "influencer." He generates a little income, but he's not desperate either.
This is what the menu on my YouTube account looks like. Do you see any "techniques" being used?