Guilliman comes back and heads home to have a heart-to-heart with Dad and takes the reins of the decapitated chicken-horse thing that is the Imperium.

Cawl pops out hundreds of thousands of Primaris and new toys that surpass anything the Imperium currently has.

In fact Cawl's apparently got so many Primaris that he can entirely restock extinct chapters and the severely depleted BA+their successors who were more than just a coat of paint and six sentence blurb. (The Primaris Lamenters got lost in the mail probably)

That's a very particular interpretation of how things went down 'till now.

Post-Godblight it's pretty clear that even Guilliman he's very unsure of what happened inside the Throne room; he heard some things, but Valoris was there and saw a distinct version. He's getting resistance in every single front, Chaos is attacking everywhere at once, the Imperium came close to losing the last stable Warp path out of the Solar System.

Yes, there's a fuckton of Primaris. They are untested soldiers, trained in virtual scenarios, and even 12 years into Indomitus, most chapters have little clue how to properly integrate them...

The numbers of Primaris is indeed fantastic. It's a pity they're dropping like flies