Belichick won 6 Championships as a Patriots HC- But will not get in, 1st try. What are your thoughts?

WHAT?! Bill Belichick is not a 1st ballot Hall of Famer... yes, you read that correctly. Belichick won 6 Championships as a Patriots HC- But will not get in, 1st try. What are your thoughts?
What's the reasoning? Personal grudge? Brady?