Complex sentence: After conversion to Christianity (something unimaginable a few months ago) the group records "El Fin De Los Inicuos", but the fans could not believe that the aggressive and heavy musicians that they had admired were singing Christian messages.
Split into simpler sentences: After conversion to Christianity (something unimaginable a few months ago) the group records "El Fin De Los Inicuos". But the fans could not believe that the aggressive and heavy musicians that they had admired were singing Christian messages.