If it is on casters moving a thousand pound object isn’t that hard.
I have a safe the 1/4 the size, that I know weight's approx 2000 lb's, (bent a 1/2 ton ram trying to lift it) and is on caster's, (a mover's dolly) and it take's a lot more man power just to move it. It's sitting in my shop, on a level concrete floor, and you don't move it like he did.