Red Semi-Tractor Trailer simply have a weight in the rear so it can wheelie easily. It's very much like a clown that wheelie small car which have several cannonball weight that rolls to rear.
Rest of others cool!
I've watched Monster Jam in Sprint Arena in KC Missouri. To be honest, it's small and truck do not have room to unleash destruction. I wish they use KC Cheif staduim which is way bigger and more room for destruction plus crash and burn Monster truck.
What changed was the exhaust noise. I was there in Kemper Arena in KC Missouri back in 1984 and the Monster trucks and Tractor Pull was extremely loud that you can feel strong vibrations from engine even backfiring. The thunder of engine kinda pass through your body. Woot!! It was more wild than today standard.
Catty