How does a search engine control this? Did it extract it? Does it search some recipe database instead? I'm confused how using Kagi netted this as this seemed to just be a defect from SEO. Is it just that Kagi doesn't promote pages like that so you end up getting the ones that don't have it?
No, it just had an allrecipes result at the top. Maybe they mark some recipe websites as good? Maybe they put less importance on quantity of text. Maybe they are not motivated to send me to a page where I need to scroll through a blog post (and ads) to get to the ingredients/steps.
One of the things they do is have the number of trackers on a website affect its ranking (negatively). I imagine that is an effective signal in cases like this.