Flybe v2 had limited cash resources... so anybody owed money by Flybe v1 was maybe unlikely to try pursuing v2 for v1. Had the claim succeeded, every creditor of v1 would then make a claim against v2... followed by v2 immediately collapsing and creditors seeing just a few pennies in the pound for any debts.
AF-KL and LH are rather larger with much deeper pockets, along with the implicit Govt backing of their respective Governments.
If AF-KL or LH were to buy Flybe v2 out of adminstration... I wonder if any large Flybe v1 creditors might want to have another go at getting their money back ? I'm sure there's a legal argument to be made...find a clever KC, and see what can be achieved...