Seibold needs results before Daly retires. He's sees that to be more likely with Brooks than Fainu who, obviously, will take some time to be a huge difference maker. He needs to win now.
The Brooks signing (kinda) gives them a transition plan post DCE and with salary cap pressure, carrying an expensive untried rookie for two years until his time comes is too much of a squeeze.
We don't have that cap pressure and we don't have any sort of halves, much less a logjam, so from that perspective, I think for Manly it does make some sense.