A veteran of one war or another, Garrett Clancy recruited him- for when he needed muscle. He's not a thinker, though he is shrewd, and he has a memory that many underestimate, and makes up for his mindset in many cases. When Clancy was killed, there was no one in a position to take over for him, making Kirina the de facto choice for Head of Station Security. No one was happy with the choice, and Kirina remembers that. He has built up the station's force, and developed relations with the major players to keep a relative peace. When the pirates arrived, he was woefully out of his league- though to be fair, Clancy would have probably suffered from the same deficit. Though he sees the hiring of an outside firm as an affront to his capabilities, he has been trying to work with Hewett, in contrast to his usual brusque approach to diplomacy. He sees the contract as hopefully a temporary thinng, and thinks that if he works with him, he can get rid of the need for that contract.
History
When Vastil heard that there was a merc company coming to the station, he was already predisposed against them. After all, he's the security lead for the station, and this was a direct affront to his capabilities, nevermind that he was out of his depth. He wants the Mercs off his station, and working with them is the best way to do that.
As contractors do, Archer just wants to get this one done for a paycheck and a good mark on his record for his first posting. He sees Vastil as a necessary evil. Though Vastil doesn't believe it, Archer wants this to go well and to be able to turn the station back over to him, so he can get a more cushy posting closer to the core, or even better in Sol. He's determined to make things safe here and make Vastil competent- or make his successor even more competent.