I haven't made it down to the Q in awhile, so I was unaware that the Cavs have been playing Rick Astley's "Never Gonna Give You Up" at the end of blowout wins.
"Never Gonna Give You Up" of course is the Rickroll video, so it's kind of amusing, I suppose, if the Cavs intentionally picked that song because of some tenuous blowout/rickroll connection.
HA HA, you got so blown out you might as well be rickrolled, sucker!
It's the same sort of endearing hokeyness behind the LeBron is Really, Really, Really, Really, Really, Really Good website and Dan Gilbert's riffing on the Combine Two Words to Show How Really Mad You are theme with shamockery, etc.
If they selected it because people are inclined to dance to classic or because they think it's a classic in the first place, I support the idea fully 99% less.