The remaining got their nuts blown off.
Probably a lot of these dead guys did, too. Any explosion that castrates a man is likely to do a lot damage to surrounding tissue as well. That additional damage could very possibly be fatal. Emasculation by explosion would be a serious trauma that calls for immediate medical attention even if the wound is limited to the genital region. The femoral arteries are close by and damage to either could be life threatening.
And 500 are blind, rendering them permanently out of service.