Complex sentence: He was a major player in the Tudor court until he advised Henry to marry Anne of Cleves, by which time he had amassed many enemies, who were able to bring charges of treason forcing his eventual arrest and beheading.
Split into simpler sentences: He was a major player in the Tudor court until he advised Henry to marry Anne of Cleves. By this time he had amassed many enemies, who were able to bring charges of treason forcing his eventual arrest and beheading.