All things were stacked in favor of Britain - ARMS support would have been inevitable. Britain had better allies, a better economy, more troops, better troops, more resources... It would have been bloody but the Manx would have fallen. Russia certainly wasn't going to help the Manx, the Pope wasn't, and Granada's alliance likely has lapsed by now (never mind they quite enjoy their secure neutrality). PATO's not going to care, Japan wouldn't, and Indonesia would have its hands tied with Malay and a decaying HITSGDP.
Most defensive alliances this game have been pretty worthless when actually pressed. No matter how one slices it, the Manx lose. They keep Newfoundland and the Falklands due to PATO's "America for Americans" policy, but everything else is pretty much done for.
The Manx enjoy a consolation in the nuking of Brussels and releasing a deadly supervirus on the British and likely much of Europe by consequence.
As for Libya/Egypt: it was couped to the Papacy as a new Republic.
I specifically stated players could give me a rundown of their plans, but the epilogue was mostly based on what could be seen. While the Emperor would not surrender, I didn't say he did; I said he fled to an area where Britain couldn't touch him. This is the logical move in a war that simply cannot be won, at least in the short-term.
The result would have been the same if it were Byzantium or Poland that was suddenly invaded. Maybe a few WMD would have gone off but they would have been defeated.
Hence, I politely suggest flinging accusations of "Bad GMing" be avoided.