Wasn't sadaba year Transcend? (as in the campaign)
Possibly. I have heard some people suggest it relates to Sync. If memory serves, the sync drive takes the flotilla to somewhere where some Vasudans are openly hostile to you, whereas some are friendly (or at least neutral) to you whilst being hostile to the other Vasudans. IIR it doesn't explain what is happening since being left thinking 'WTF is going on!?'
is kinda the point in Sync (and Transcend).
However, since we now know that the multiverse theory is true (within FreeSpace at least), we can perhaps better understand what was happening in Sync. I suspect what the sync drive actually did (unintentionally, at least on the part of the humans*)
is take the flotilla to one of these alternate realities. In that reality perhaps the HoL were not defeated militarily, and were continuing their civil war against the GTA / PVN / GTVA etc. That would explain why some Vasudans are hostile to both the Terran flotilla and to the Vasudans who were not
hostile to you. These aggressors being the HoL. It has been a long time since I played Sync and I only played it once, so I might be misremembering somewhat. I feel another play-though coming along
*Of course this does beg the question "Was it actually an accident?"
Considering t2's apparent ability and willingness to pull fleets from one 'manifold' to the next during 'unusual' hyperspace jumps, could the events of Sync have been deliberately engineered? Could it have been a 'dry run' to test if they could move ships and their squishy human crews from one manifold to another without damaging said ships and crews, (perhaps both physiologically and mentally)? Could Sync have been t2's 'warm up' for what they would later do with the 14 Battle Group?
Now there is some juicy head canon material