Your first two reasons are why they're discontinuing support for Windows 10. The intention to drive Windows 11 adoption is inverse to disabling upgrades, because then some of the people without a supported PC won't be able to afford a new one and will switch to Linux or continue to run Windows 10 unsupported when they would otherwise have installed Windows 11 on it.
And the security reason is nonsense because as you point out, the overwhelming majority of Windows security problems are in no way improved by a TPM.
The most likely real explanation is that Microsoft is constantly at war with itself and the manager currently occupying the relevant coign of vantage finds it to be in their personal interest for some muddy reason having to do with internal politics.
And the security reason is nonsense because as you point out, the overwhelming majority of Windows security problems are in no way improved by a TPM.
The most likely real explanation is that Microsoft is constantly at war with itself and the manager currently occupying the relevant coign of vantage finds it to be in their personal interest for some muddy reason having to do with internal politics.