At first, it was not obvious why they were surviving, as there could be many reasons; fighters might not be able to see them against the ground, AA guns positioned inland might not be able to aim at them, etc. But it quickly became apparent that low altitude flight meant they were not being detected on the radars.
Initially, there was no obvious explanation for why these aircraft were surviving; fighters might not be able to see them against the ground, AA guns positioned inland might not be able to aim at them, etc. However, it quickly became clear that low-altitude flight meant they were not being detected on radar systems.