If anything, I think it's more likely that the Blood Spirits didn't quite put all their eggs in one basket (ie why not a remote outpost or colony) and/or there were various units/merchant case/etc that weren't in the system when this all went down. The writing was on the wall for a very long time that the Adders were likely going to eventually wipe them out and that there was nothing the Spirits could do to halt it really. Even the retreat to Colleen was little more than some time bought to the unstoppable Adder menace. The Spirits had been attacked & bled by the other Clans for a very long time and most of their "allies" were gone or had left.
Of course, Battletech is full of people/governments/etc that ignore the obvious for narrative reasons, but the Spirits should have been able to forsee a potential annihilation - or the least that they'd lose all their assets (which happened before the Adders' "absorption" to some extent anyways). As such, it's logical that they had a plan B - even if it was potentially a very weak plan B. They just had to sell their destruction and it had to be common knowledge that they'd never be able to escape with the bulk of the Clan.
The Jaguars, Nova Cats, Clan (Jade) Wolf, Wolverines, etc are all examples of Clans that should be gone surviving. The only ones to truly stay dead might be Mongoose, Widowmaker, and (maybe) Burrock. But even Burrock had their own return - and could even still exist. It just depends on what Catalyst wants to do with them. There's certainly a ton of plot hooks out there in the Clan homeworlds.
