My gut reaction is that this highjacking was "opportunistic" and "state sponsored". The "actors" knew there wouldn't be any consequences.
It would be nice to "send a message" by banning an AS number. The hassles involved in revoking that ban and/or obtaining a new AS number would make it unlikely that such opportunistic bad behavior would recur very often.
...but what if they make a request under the guise of a different organization, to be assigned new numbe--
ONCE AND FOR ALL.