I used FreeCAD to convert your STL into a 100+MB STEP file and was able to have Solidworks begrudgingly open it. Also uploaded it into an Onshape document. Here's a link:

https://cad.onshape.com/documents/a1...38566c743839bf

You may be able to pare it down more easily in Onshape since their cloud servers are handling the heavy computational lifting. I don't have time to mess around with it too much, but it's there if you want to take a crack at it.

Here's the workflow I used to convert the STL to a STEP in FreeCAD:

https://all3dp.com/2/stl-to-step-how...files-to-step/