Why the sabotage counterfactual selects British ASDIC

If forced to sabotage one British or Allied program after 1930, which project would most help the Axis?

Sabotage British sonar development; unlike the many parallel radar programs, ASDIC was a concentrated capability whose loss would seriously weaken convoy escorts.

Radar is rejected as the sabotage target because many services and countries pursued parallel programmes. British sonar, or ASDIC, was a narrower programme whose disruption would directly weaken convoy protection and attacks on submerged submarines. Sabotage would not guarantee an Axis victory because Allied industrial and logistical advantages still favored a long war. It would give U-boats a larger operational edge and make surface escorts much less effective against them. Timing matters because sonar development was already progressing through the 1920s and 1930s.