He was well liked by players, he coached a dozen guys into high draft positions, he has the NFL credentials himself now, he knows Bud's system extremely well, and he would be a recruiting asset... Your argument is weak to say the least - all first time DCs were only position coaches, all first time head coaches never had prior proof they could do the job. Dabo went from position coach to head coach in a year. TG is one of the most qualified positions coaches around.

People like hiring alum because it's less likely they are just going to jump ship the next time someone offers a few more dollars.