I'm not an expert or anything, but is this making the assumption that there is 0 loss? You put 1Kw into a microwave transmitter on earth and expect to get 1Kw out of the receiver on the moon?

That's preposterous - I would be surprised if you get more than 5% of the power considering the losses in the transmitter, receiver (and related circuitry), not to mention the atmosphere itself plus whatever little bits get in the way (like, I don't know, the thousands of Starlink satellites and other space junk).