You haven't explained Capella...
I'm guessing that they felt cornered, and decided to turn Capella into a temporary jump node to escape (and conveniently destroying a huge number of their enemies in the process). It seems like a good move: you get some of your ships out (which probably have the rest of the ships crews on board, or maybe they even ran the juggernauts that got destroyed by remote) and do severe damage to the foe at the same time. Its also quite possible that they can build ships in a very short time, and possibly have a sub-race dedicated to flying fightercraft that matures in a much shorter time (thus allowing them to use swarm tactics VERY effectively), so they didn't loose much. We never really see how advanced the Shivans are compared to the GTVA, outside of the ships themselves, so this is quite plausible.
(I'm getting some inspiration from Arther C Clark/Gentry Lee here. I just finished reading the Rendezvous with Rama series.)
I'd be surprised if the Shivans felt cornered by the GTVA. 80 juggernaughts could wipe out the GTVA as quickly as each could jump to each of the GTVA systems and flatten everything in their way. Lets assume that the GTVA could be successful at somehow disabling or destroying even a handful...heck lets go half way and say 40 juggernaughts destroyed, disabled, or severely damaged and out of the fight...there are still more uber killing ships of death than there are GTVA systems to destroy.
Capella was probably very little about the GTVA and more about some sort of overriding goal or objective that required destroying a star. My theory is that it was some sort of subspace bridge or temporary supernode. The remaining juggernaughts jumped away...destination is unknown of course.
I don't mean they felt threatened by the GTVA's ships. I feel they may have been threatened by the GTVA collapsing jump nodes. Remember, they had 80 or so juggernauts in the system. They may have felt the best course of action was to set off a supernova in the system. Why?
1: if the GTVA was going to set of another Menson bomb, they would probably have their ships leave first. And even if they didn't, the ships would be just as worthless. No need to destroy something that is already unrecoverable. (I'm assuming that the Shivans do NOT have intelligence on how the GTVA is researching the Knossos portal to stabilize jump nodes.)
2: if the ships where gone, and the node closed, destroying the star would be a waste of Juggernauts. And even though fighters are expendable, a juggernaut is not nearly as easily wasted, never mind how many that couldn't get out. The Shivans where maximizing their ship's value.
I just finished reading the Rendezvous with Rama series.
Heh... I'm in "The Garden of Rama" right now.
Ouch!
Isn't it all a bit downhill after the first one? Gentry Lee doesn't seem up to snuff.
It's not that bad. They ARE another author's work, after all. And I agree, they aren't as good as the original Rama.