Honestly this might sound rude but a lot of written tutorials/blog posts in JS are made by people with good intentions but not a lot of experience or expertise,

Honestly this might sound rude but a lot of written tutorials/blog posts in JS are made by people with good intentions but not a lot of experience or expertise, so they end up hand-waving a lot or just not explaining things right. The linked video is by a long time, well-respected frontend developer.