That made me chuckle, considering that Kerwin is partly to blame for their destruction. Sure Rieleston would have likely gotten involved at some point, but Kerwin's presence in Heorot sealed (RP-wise) Rieleston's early involvement.
I still don't buy that reason. Were all of the realms currently destroying Heorot planning to attack the Barony? Considering how much time he spent in the Barony just before the split, it didn't seem such a pressing issue for everyone before Heorot was formed. Or was someone making plans to kick Kerwin out of BoM?