I experienced a power surge at my house and some equipment stopped working. one device just had a blown fuse so I soldered in a new one and it worked fine. Another device had an obviously blown varistor and another one that just had a crack in its outer shell. I found the 07D221K and replaced it but couldn’t find the 10D221K so I replaced just the one. This didn’t fix the issue. Is a varistor with a crack in the case a sign that it’s also toast? I also replaced the fuse.
A crack in the surface or coating of just about any components is an indication of stress, mechanical, thermal, electrical, etc.
So it's probably a safe assumption that your cracked varistor is bad. What is not clear is which OTHER components were damaged by the same surge that took out your varistor.
This didn’t fix the issue. Is a varistor with a crack in the case a sign that it’s also toast?
It's not a good sign and it may well be broken but, given that both varistors mentioned are across the supply i.e. they are rated to withstand 120 volts AC power voltages, then it's unlikely that replacing it will fix the problem i.e. something else has blown.