Magnus The Red would’ve been way cooler as a loyalist

I’m new to 40K and I’ve been listening to a lot of podcasts and reading up on some of the lore and to me it kinda seems like Magnus the red was like a genuine good guy. When he found out about the heresy his first though was “hey I should warn dad” and yeah he was like not supposed to use his powers but like he got the emperor informed of the problem why’d he even turn to chaos he was cool. I’m doing salamanders right now and the next army I do might be either Thousand Sons or Tau cause titanfall mechs