It's a short term budgeting issue. The German government is struggling on that front.
It's interesting then that they fast-tracked the purchase of the six C130Js and prioritized this over starting a buy of heavy lift helos, given they have the all singing and all dancing A400Ms inbound. Think of how much more useful hardware they could be buying if they weren't subsidizing Airbus to make A400Ms at a loss.
It's got little to do with priorities. First of all, the helo program is a much larger project that requires the allocation of long term funding before the Bundeswehr is even allowed to select a type. The long term budget plans got delayed as there was no working government for too long, and one of the coalition partners isn't keen on a huge increase of military spending.
On the other hand, since some other programs like the A400M and the new frigates got delayed as well, and consequently didn't have to be paid for, there is some money left in the short-term budget, which is just enough to buy a few C-130Js that supplement the A400Ms (which actually are quite useful, in spite of your constant bashing).
Of course the priority of the C-130J is enhanced by the fact that it's a common German-French project, where France has already done the first steps. Maintaining so few machines of a type would be inefficient for one nation alone, and if Germany would step out, it would be harmful for the international relationships.