Complex sentence: It might have seemed easiest to bring back the Kapitän first, since its engine was already in production for the truck, but occupation regulations restricted German civilians to cars of 1.5 L or less, which made the Olympia the obvious candidate.
Split into simpler sentences: It might have seemed easiest to bring back the Kapitän first, since its engine was already in production for the truck. But occupation regulations restricted German civilians to cars of 1.5 L or less, which made the Olympia the obvious candidate.