Ask HN: Long landing page or multiple pages?

I've noticed that some startups use very long landing pages that seem to describe every feature of their product. I look at those and think they should really be split up over multiple pages. I'm wondering if anybody has any insight as to why those are becoming more popular? My speculation is that it is for SEO purposes and that somehow one page covering everything is better than more targeted pages covering individual features? I'm seen some guides that imply the latter is a better way to optimize which implies long landing pages are bucking the trend.