People bonk because they're not eating enough DURING the ride. I'll eat (actually mostly drink) like 120-200g carbs on longer rides. Record is 700g during a 200km ride. I've seen big guys bonk too. It has very little to do with your BF% (although this is nuanced based on power zones and training 'durability' etc, etc).
Going back to my endurance days, I think people bonk because they aren't adapted. After a year or so of pushing through the bonk, and growing up with hypoglycemia if I didn't eat frequently, I got to where I could start out at 5am on an empty stomach and not eat until noon or later. If I did bonk, I'd sip V-8(yeah, really) and instantly recover.
Yeah this was the attitude back in the day and I know some older guys with this mindset but the science on this is pretty clear.
It’s definitely one of, if not the most, currently focused on aspects of endurance sports outside of the actual training.