[sandworm101]

Almost. 2.4GHz had been set aside for consumer devices long before wifi. Microwaves are essentially very powerful unlicensed transmitters. Wifi devices are also all unlicensed transmitters. So 2.4GHz devices don't use the same space despite microwaves, they use it because that space had already been given over to unlicensed devices. If not for microwave ovens we might not have wifi as it is today.

Back when people were gobbling up the spectrum, the military didn't care about 2.4GHz because of the water absorption issues. It wasn't good for communication at long distances and so it was allowed for consumer devices.