Let me start with. I HATE YOU YOUTUBE!!!!
YouTube is always changing the rules. One trick I used to use with GoPro and other action cameras is shoot in 1080p at 60fps. This gives you a small enough file to work with and still look really good on any size monitor/phone.
Well YouTube decided that if you upload in 1080p they encode it with a crappy AVC codec instead of the nice VP9 codec. That is unless your video gets at least 1000 views. Then your stuff looks better. UGH.
Anyway, sorry about the crappy quality.