Mehrunes Dagon is not only the Daedric Prince of Destrution, he is too the prince of Change and Revolution - elements I think sometimes get overlooked. It's plain to see the amount of change and revolutions/wars that have occured shortly after the Oblivion Crisis in direct relation to it.
1. Black Marsh succeeded from the Empire after it failed to protect it from the Forces of Oblivion, leaving the An-Xileel to defend the Argonians and close the Oblivion gates themselves. The An-Xileel now rule an independent state.
2. Morrowind was conquered by the Argonians shortly afterwards as revenge for years of slavery by the Dunmer (Although now it seems at least parts of Morrowind have broken free of their control - but nether-the-less still not part of Cyrodiils Empire.)
3. Summerset Isles, again the Empire left them to defend themselves so the Aldmeri Dominion stepped up and, like Black Marsh, left the Empire.
4. Valenwood joined with the Summerset Isle to make Alinor after some battles, leaving the Empire.
5. Elsweyr left the Empire and now support Alinor after the Thalmor 'allegedly' brought back the moons after the void nights.
6. Hammerfell left after the Empire agreed to give half the province to the Thalmor, although it is now a independent province, after forming a stalemate with the Altmer.
7. The civil war in Skyrim, due to the banning of Talos by the demands made by the Aldmeri Dominion after the White-Gold concordat.
Mehrunes Dagon must be laughing his ass off over in the Badlands after the amount of revolutions and shift of power that occurred as a direct result of his 'failed' invasion. I don't think this has been mentioned before. It probably has, but maybe some missed it, I dunno. it's just rather funny and a little ironic that 2 parts of Dagons aspect have actually ultimately succeeded even if by accident.
- There may be a few mistakes, it's all from the top of my head, but I'm sure you'll get the point of it anyway.