Bodybuilders eat a lot in the offseason because they're on tons of drugs and trying to maximize the amount of lean mass they can put on, and they eat more in general because when you have 100lb+ more muscle than the average person you have a significantly higher base metabolic rate. You can go on a variety of PED related forums and find IFBB pro's posting food logs, etc., and see that these crazy eating routines are limited to certain parts of the year, and even then have been falling out of favor - the 'lean bulk' for pros is more popular than ever.

Very few IFBB pros are working out in 2 hour sessions, either. Coaches understand junk volume way better now and know that a lot of the work being done previously just wasn't providing much muscle growth stimulus after a certain point. Most are spending <8 hours in the gym each week in general.

The top of the bodybuilding field is not eating a ton of food because of their lifting routines burning a bunch of calories.