You don't think Pop was aware of Tony's demise?

Pop was simply playing the loyalty card & was back paying Tony (someone who he treats as his own son) for taking pay cuts during his prime (most likely a handshake agreement). You also have the issue of finding a replacement that Pop is willing to trust right away since Tim/Manu are nearing the end of their career not to mention Tim/Manu might have vouched for Tony & might have retired if he wasn't retained.
After 2014 Pop basically didn't give a about chasing trophies b/c there was nothing that was going to top it so he main focus was ushering in a new era while allowing the Big 3 retire on their own terms w/ their dignities intact.