If you right click and go to 'Stats for Nerds', it shows 30fps and lots of dropped frames. Extreme foliage loves to eat bit rate but while 60fps would generally show more detail, I hear that 1080p 60fps looks like crap on the Mavic, so... limited options... and I suspect that youtube makes a lot of adjustments in an effort to try and "fix" the upload. Youtube reencodes all videos regardless of the upload format. vp9 (Google's compression codec) is notorious for causing issues too. Chrome also renders videos much worse than IE11.
In the end.. Probably best to shoot 2.7k 30fps, don't zoom in more than x2, and export to 1080p 30fps.
Great shots though. Enjoyed the vid.