I was getting message after message: "We've been well paid to take care of you" until every race but the Drath had declared war on me. It's pretty obvious who was responsible for the bribery.
BUT . . . I was playing the Altarians. And every time the Drath bribed someone to attack me, they would have to declare war on them in response thanks to my super ability. In the end it was me and the Drath vs. everyone else.
Maybe they wanted to be at war with everyone and needed an ally.
Similar thing happened to me early in my current game: playing as Altarians with Drath as neighbours (I always end up next to the bloody Drath, and they always take offence). Got a message from the Iconians, declaring war becuase it had been made worth their while. Drath feel compelled to take my side. Then they start giving me ships... lots of ships. Some warships, but also a space miner and a brace of advanced constructors. The thing is, the Drath didn't actually have a military of their own, and therefore were trading me ships that they presumably had bought at some expense from other parties.
It all worked out OK in the end though, Iconians are now my best buds and the Drath and I are getting hammered by Drengin. Annoyingly, I was dragged into the war by an alliance and therefore my ability didn't kick in when I actually needed it. So it goes...