Question

Why did the can not become instantly crushed when plunged in the ice water when it was heated without any water inside?

Answer 1

Because since there's no water in the can, the cold water outside of it didn't have to equalize with the missing hot water that's missing from inside the can. if there was hot water inside the can then it was plunged inside the ice water, there it would have instantly been crushed.

Hope this helps