I understand that the first cosmological computer simulations Did not have DM Only gas dynamics on expanding grids And, that those sims produced no structure of any kind No LSS Only vast expanses of nearly uniform space plasma Devoid of any clumps Essentially reminiscent of the real actual voids Which fill about 3/4ths of the volume of space So simply stated, the first earliest computer simulations Accurately reproduced VOIDS ... In some sense they were 75% accurate... But they never produced the large scale STRUCTURE Particularly important to people upon this planet? Hence the motivation for " something extra" ( people inserted DM ) to cause clumping into galaxies and clusters etc??