Neither did Gibbs lol. He waited 4 years.
Part of it is that coaches are sort of in a separate more congested category than players and the spots are limited and the waiting period for coaches has changed constantly. It used to be very little so they didn't care about first ballot to get some guys through because coaches already weren't waiting the 5 years. Then Gibbs got in after 4 years of retirement and then came back in the league and they didn't like that situation so they changed it to 5 years. Now it just recently got put back to 1 year and they are in this crowded and congested category where it sort of feels like some guys are skipping the line over guys who waited forever.
A big problem also is they don't really know what to do with coaches as a category. There's such a large amount of players that they can fill a class every year, so if you put coaches with them, even some of the most deserving might get passed over because players really are the the priority. You can't have a separate category for coaches alone because there just aren't enough coaches who are HOF worthy to merit it and even being forced to have 1 each year would completely dilute the whole thing. So they get stuck with contributors and the vets where the intention is to take older historical figures who fell through the cracks or were harder to contextualize in their time but are deserving. Roger Craig is a great example because he was probably a very borderline guy in his era but was fundamental to a dynasty and time has been even kinder to him where people view him as integral to his team's success, so that borderline case that just barely missed it is now tilted in his favor and because he needed that historical perspective, he is now part of the vets.
But Bill's stuck with guys like that who waited forever and realistically because they changed it, some of them are going to get crowded out again because more recent coaches and contributors will start popping up.
I don't doubt that there were some people that just used Spygate or wanted to punish him for how he was to the media. But that other aspect was the rational of at least one voter and so you add that in and it opened the door for something like this.