Yes, this is a problem with scaling. The bounds of the grid data goes from 0 to 127 in each dimension whereas the bounds of the points go from 0 to 50,000.
I’m pretty sure the problem is with the grid data. A uniform structured grid has an origin (the position of the lower left corner) and a spacing (the size of each cell in the grid). The default spacing of a grid like this is usually 1 (for lack of a better value). That is probably wrong in your case.
There are multiple ways to fix the problem, but the best would be to fix your data file. You can do it for your HI_8_128_grid.vtk file by opening it in a text editor and changing the 6th line from
SPACING 1 1 1
to
SPACING 393.7 393.7 393.7