They could use that computing power to mine blocks, and it would give a bigger gain in their life time, than trying to find matching private keys.

It would just be a pure fluke, if they do match up a single address with a private key, and by that time, they would have wasted a lot of money on electricity cost.

Let them do this, and show how secure SHA 256 is, if they did not solve it in 50 years.