This has been a topic for a while now, we are talking about years, and not a single thread has the answer. So lets finally solve this.
Why only the first chain of simulated bones behave correctly and all the other ones snap to root?
The answer so far I have found that works is to set Blender unit scene to 0.01, then scale the bones until is big enough like, 10 or 20, then apply the transforms with Ctrl + A > All Transforms (or at least the scale) and it works, but it seems unnecessary, even the pipeline Send2Unreal tells you that setting it to 0.01 is not a good idea.
Any other solution?
Okay, looks like Unreal Unit system is in Centimeters while Blender is in Meters, that explains why changing blender to 0.01 fixes the issue.