I saw a post on Reddit from a Bills fan that said Digg set the culture at the Bills when he arrived. He was a perfectionist and really demanding of Josh Allen, would make the offense practise routes over and over until they got it down.
The problems, or "diva behaviour" started when Josh Allen became a star and was less inclined to be led by Diggs. Diggs complained about him not being commited and being half assed about preparation and distracted by his girlfriend and their relationship broke down from there, to the point where Allen wouldn't pass to him if he could avoid it.