>>96396470
Perturabo ran away? Literally how? The airspace wasn't safe for an evac, not with both the IF and UM fleets.
Perturabo was there because he NEEDED to ascend to daemonhood, and this he achieved by bleeding the Fists for it on a fortress-sized summoning circle.
The Target of Opportunity was Dorn, and the lives of every Imperial Fist. But Guilliman arrived, so Perturabo wasn't able to get this. Oh well, primary objective had been achieved already. Next time. And now he had eternity to do (or not do) whatever...