You have already decided that the ignition switch is bad.

However, if it were me, I would check my cabling at the battery and be absolutely sure that I was getting 12V to the fuse box and the ignition switch before I condemned the switch.

If you are correct, and the switch is the culprit, the tumbler is not the problem. The problem is in the switch contacts and it would need to be replaced.

BTW, electrical issues rarely give any warning. They will be working fine on Saturday but the vehicle won't start today. No surprise there.