France was defeated in Europe, so what else can a colonial government do but to surrender to the Japanese ? But this is nothing more than a feeble attempt at distraction.
Ho had no authority to do so. He was not representative of the Viets.
Legality had nothing to do with it since Ho was not authorized by anyone, least of all by the Vietnamese people, to make any treaty. But you should really stay out of the Vietnam War discussion since you are wrong about this fact.
Ho–Sainteny agreement - Wikipedia, the free encyclopedia
Ho Chi Minh was the leader of the Viet Minh.
Invoking legality was a hilarious attempt to salvage face for you since it is clear you did not know of the Ho-Sainteny Agreement.
In sum, the cause of the Vietnam War came from two sources: China and France.
China had no obligations to do so.
So was the US and the US was fully behind the idea of booting France out of Indochina. Chiang Kai-shek agreed. And there was no way Mao was ignorant of this consensus since Mao had allies inside the Nationalists. In sum, Mao knew what the US would do to Indochina -- UN trusteeship towards independence.
I brought up treaties only as a question as to why China meddled in Viet Nam. If you feel that ideological alignment should be and must be enough for countries to get involved in the affairs of other countries -- say so.
Again...Ho and the Viet Minh had nothing to hold over China's head. If you are wiling to blame US for Iraq's current mess, then in the same logic, we can blame China for the Vietnam War.