Why my youtube videos are in low quality when watching at 360p

[chathuvv]

Can some one explain me Why my youtube videos are in low quality when watching at 360p.
But I have seen other videos at youtube are in better quality when watching at 360p.

I always capture videos in 4k and render thru primer pro at 1080p (or a inbuild preset at PP)

 

[Amila llll]

low bit rate

 

[chathuvv]

I usually use the default bit rate. I think its 30 or 40.