>Instead they are made out of superconducting materials which have basically zero electric resistance.

There's a pedantic but critically important bit here that super conductors have actually zero resistance as long as they're below their critical temperature which means they don't dissipate any heat which is what lets them carry the crazy currents needed for the strong magnets

As soon as any part passes the critical temperature its resistance becomes not zero, it starts dissipating a ton of power, the helium nearby flash boils, more of the magnet heats up, and everything comes crashing down in a sad magnetic quench that tends to damage everything

So the magnets are cold because if they're not super cold then they're resistors not magnets and they instead get super hot