Check out the lore tabs on the Spire of Stars raid armour and weapons. Those would be available at the Ishtar collective website, and I’m sure you can find the names of the gear items through a google search of Spire of Stars rewards. Basically, after Ghaul’s death, the Cabal command chain was decimated. Most of the existing Valuses were deployed to re-establishing and holding the Exclusion Zone on Mars, and expanding into Hellas Basin. With them all out in the field, the most charismatic original officer was Val Ca’our. Due to his influence and persuasion, he ordered around those Valuses, sending Valus Thuun to secure Vex technology and weaponry on Mercury, and the rest to secure Mars and find Rasputin. He then used most of the remaining Red Legion fleet to try and claim the Leviathan, defeating robot Calus just as we did, but being foiled by Guardians before he could settle in. From what we know of him, we can assume he’s been in power since almost right after Ghaul’s death, as the Inverted Spire strike is yet another attempt to use Vex weaponry to Cabal advantage, and he specifically refers to plans that were carried out at about this time. Hope that helps.