The Germans did not initially understand that captured men belonged to a kayak raid, instead apparently treating them as scouts for some other commando operation. That misunderstanding helped preserve the attackers' method and objective until the mines detonated. Sending a second submarine and twice as many kayaks would have increased congestion, coordination demands, and the number of chances for the craft to be discovered. A much larger insertion might therefore have sacrificed operational ambiguity without proportionally improving the chances of success.
Notable Point · 1:30:40-1:32:54
Why simply enlarging the raid might have failed
Sending more submarines and kayaks could have produced diminishing returns by making the force easier to discover and revealing the true nature of the attack.