The catch here is that Selleck never actually turned down the role. The mustache himself set the record straight on Letterman, laying the blame at the feet of CBS:
“They held the offer out about a month. And the more they held out the offer and talked to the network, the more the network said, ‘no…’So I go to Hawaii to start Magnum, the actors go on strike, and I had given my deposit to a landlady and I couldn’t afford a security deposit. So I start working as a handy man, in Hawaii, with no job. And guess who comes to Hawaii to finish their movie? Raiders of the Lost Ark. So I could’ve done them both.”