PR, nadeys, похоже на правду. Непонятно только, почему не добили.В каноне как раз есть намек на обратное:

“The attacks on them came after Voldemort’s fall from power, just when everyone thought they were safe. Those attacks caused a wave of fury such as I have never known. The Ministry was under great pressure to catch those who had done it. Unfortunately, the Longbottoms’ evidence was—given their condition—none too reliable.”
На министерство "давили, чтобы они поймали виновных", значит виновных НЕ схватили на месте преступления.