Elementary reading skills would also make it obvious that I'm not talking about their move from and back to DC. Them moving back and forth from DC is certainly irrelevant to WaPo's quality.

They noticed a decline in quality from before and after the acquisition and are using that to conclude that the acquisition didn't impact the quality of the paper. Again, that certainly seems like a strange way to make the point that the purchase didn't impact its quality.

... because they left DC before the acquisition ... and moved back to DC after the acquisition ...