Thanks for reaching out, and sorry for the delay in responding.
Well, Daniel is right, this was made before the Physics came into the picture, and the only real secret is that Hype is simply an amazing program
But if we talk more in details:
The character is made with several layers, which have all their movements keyframes in a separate timeline. The Legend's timeline is triggered to start in a specific time from the main timeline.
The layers in the back, are the legend's cape, and they have their anchor point on the top side (around the legend's neck), and also move independently in 3D sphere. However, all the layers move upwards and downwards "in the same time". So it feels that the cape is connected to the body, even if they go up and down together. Also, all of the layers are anchored to top and bottom of the page (not left and right) to force them follow the responsive layout.
Anyhow, with the new version of Hype, you can do this in a much better and more responsive way. If I should recreate this now again, I would put all the legend's layers into one symbol, and then move (floating movements) the symbol in a separate timeline. This would give you more flexibility, you could have more parts of the body to move, perhaps add some physics, and still make it work with your general responsive layout. I assume so at least, but I haven't tested it. The strategy you choose depends on what you want to make.
Hope I could help
Thanks a lot once again!
And let me know if you make something similar.
you'd find a more dynamic version of the legend here: https://www.surveylegend.com/404