MJB,
If there's two crook patients, it's often better to send two helicopters. That way you get two medical teams, two sets of equipment, etc. The additional cost is not high because most of HEMS costs are fixed. The flying cost is not much in the great scheme of things.
As for space in the AW139, it is actually quite cramped with two patients, medical equipment and medical crew trying to get access to the heads of the patients.
As for why partners were sent to different hospitals, it could be a myriad of reasons, eg different injuries went to different specialist units, or perhaps similar injuries meant that it would be better to send the patients to different hospitals to spread the load. Depending on the jurisdiction, hospitals will publish how many trauma patients they are prepared to accept, so perhaps there was no hospital that would accept more than one patient.
I'm not defending the actions, just saying that that they are plausible in some situations.