I agree that services flipping from subsidised to commercial is an eyebrow raising thing, especially if they then flip back. (Though that might be explained by some major change in costs or passenger numbers - the bus world has been pretty difficult since 2020.)
But basically, that's the deregulated regime that we have had since 1986. The successive operator changes on 82 under annual contracts (JH, GCT, now GNE) seem to me an extra instability that arises only from the choice that Nexus makes to award only 12 month contracts.