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I think you'll find I'm right
Well, I didn't make any points about surface area. Monster trucks are different from normal trucks in many ways beyond tyre size, and the differences are not only of an entirely different order of magnitude from the differences between fat bikes and normal bikes, but in most ways categorically different.
You are right that both monster trucks and fat bikes have wider tyres than their normal brethren, but that turns out to be pretty irrelevant.
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No, you're wrong. Fat bikes and monster trucks are wholly different, not least because fat bike hubs are by definition running in double shear, whereas monster truck hubs are in single shear. This means the length of the axle is pretty irrelevant for fat bikes, but a major consideration for monster trucks.
Your point about surface area and load is moot when considering torsion / friction.
I think you'll find I'm right. :o)