I don't buy that the cooler loop caused the oiling problem for several reasons. Fisrt off though I am assuming you saw good oil pressure indications from a reliable gauge during operation of the engine.

Automotive oil pumps are simple fixed displacement gear pumps. In the absence of controls this type pump will generate whatever pressure it needs to drive the oil through its circuit based upon what drive HP you can twist the pump shaft with. Pressure controls are usually in the form of a pump internal relief. Also the filter pad on most engine makes has a pressure bypass check valve that precludes either the filter or cooling circuit from starving the engine main oil gallery. Otherwise on cold days most people would kill their engines due to the extra pressure drop across the cooling circuit.

I hereby throw my BS flag at the cooling circuit cause of failure ......

Good Luck, Kitz