they experimented with his phasecannon to jump to other planets. They just experimented with this gun and a exotic star as a target. As the projectile hits the exotic star the star colapsed and a giant unstoppable phasewave starts running trough the universe. All things which are electrical powered or just out of metal or just technoligical advanced (not sure with this part ) are thrown into phase space as the wave passed by.
So they cant look what happend because all ships that are flying back are thrown into the phasespace as they pass the event horizon of this wave. Thats the reason why the probes from the vasari are disappearing from the radar one by one. An advanced (brained) enemy would not reveal his actual position to the enemy by destroying probes as if they can destroy them without beeing detected they can pass them without behing detected.
So, the vasari are still alive on there old worlds, but without any technologic they a forced into a new stoneage and they will need centuries to coming back with the first phasejumpcabable ships as the knowledge for this technology is lost.
There is no enemy! There is just a giant cataclysm for the known universe. As soon all factions will realize the truth, freedom will fill the TEC-Space to find a solution before the wave reach there new homes.
My idea for them to get behind this wave. the should build a giant ark that is completly out of an organic substance and store all knowledge in the DNA of the ark. After the wave has passed they can extract the old knowledge out of the DNA from this ark.
And after that: if you know your enemy the day have structure - the war begins again
greets from the other side of the phasewave
btw: you want to know how they will find out that there is this wave ? There will be some very powerful advents. They can journey long distances with just there minds (think of there capital). They will see the truth. Maybe they will need some special spice from a nice desertplanet with dunes and worms