Some collaborators had the choice to either join the party later on or openly oppose them. In germany people who joined the party after the war started are often viewed different from those who followed early on.
Just today i heared a podcast about Werner Foßmann and the fact that he joined the party in the early 30s was a point against him.
I watched veritassium for a short while, but i can’t take them serious with all the click bait. Can you provide a link to the proper study instead?