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.