I checked the timeline and saw that Slyne had a huge spike in almost everything, I don't know what could be the cause of it. The most likely explanation to me was that they had conquered someones homeworld, but none of the other factions had a drop of any kind. The Terran resistance had a similar spike in power, related to military earlier on, where i checked around for new ships since we had an exploration treaty, but I found none. I started a trade with them, and none of their ships were particularly powerful, neither were any of their starbases. I really have no idea what could be the cause of any of the spikes, it seems to me like the AI is just cheating.

Here are some images of the timelines so you can see the spikes: