Sanguinius in the Horus Heresy

I’m pretty sure this is a common question but I’d appreciate any information.

For context I grew up in the 80s and 90s and at a young age had a friend that was obsessed with painting red space marines, this is when I originally leaned of the Blood Angels.

I’ve recently gotten back into the hobby, I’ve mainly been painting but have also played some casual games with friends.

While painting I’ve been listening to the start of the Horus Heresy and have been absolutely blown away. I just finished Flight of the Eisenstein and now need to chart my path through the flowchart of novels. I’d like to follow any path about the Blood Angels but their factions (from my research) seems to be lacking in content.

I’m wondering why the Blood Angels don’t show up that much during the Heresy, but were one of the original factions that GW created? Also Sanguinious plays such a major role at the end that I’m surprised that the Blood Angles don’t play a larger role though out the story. I’d love any insights! TY

For Baal! For Terra! For the Angel!