Assuming nothing changes in terms of internal politics. Lebanon will be poorer on account of Syria’s poor economic decisions and the Syrian civil war. On the religious issues, Lebanon will see an expansion of Syria’s with the Christian, Shia, and segments of the Sunni population supporting the government.
Things would bound to be different before WWII. There already was a war/Revolt in 1925-7, 5 years after the French kicked out King Faisal, and States created under French Mandate control
Revolt ended, with the French doing much of the same pacification they later tried in Algeria
The Christians in Lebanon did not revolt, but saw the French as Protectors, local Muslims didn't see thing the same way, wanted to be part of Syria, and moved from being a autonomous state, like they were to a degree under the Ottomans, to being Independent, split from Syria
All the states were reformed back into one Syrian State before WWII, except Lebanon
Without the reward for the Maronites getting Lebanon, they will be causing more trouble