"history" in this context predates the modern era of BYU / college football - we're basically talking about one single hire that has not worked out well, in the relevant decades. Even if you want it to stretch back to Hudspeth you're at an entirely unscientific sample size of two. Not sure how that forms the basis for any conclusion that means anything at all.
What's more, I'm not really sure I'd even consider Bronco an "internal" hire, since he'd only been DC for a couple of seasons at BYU before being promoted, and spent significantly more time at New Mexico prior to that. He's arguably an external hire who just had an extended on-boarding period.