Complex sentence: Success led to the average attendance at Anfield increasing to over 50,000, the fans also became more vocal and it was around this time that the fans on the Kop adopted You'll Never Walk Alone as their anthem.
Split into simpler sentences: Success led to the average attendance at Anfield increasing to more than 50,000. The fans also became more vocal, and it was around this time that the fans on the Kop adopted You'll Never Walk Alone as their anthem.