Complex sentence: However it is unlikely that Bastard was the inspiration for the chant; it was not documented whether he wore black while refereeing, and football chants did not include verbal aggression towards officials until the 1960s, long after Bastard had died.
Split into simpler sentences: However it is unlikely that Bastard was the inspiration for the chant as it was not documented that he wore black while he was refereeing. Another reason why it is unlikely that Bastard was the inspiration for the chant is because football chants did not involve that type of attitude towards officials until the 1960s, long after Bastard had died.