Hizbullah cannot take over Lebanon militarily. The moment they decide to do that, they will ignite a civil war. And in a civil war, that means there is a side fighting against Hizbullah. That side will no doubt be supported by the West, Israel, and the Arabs. The sheer amount of resources behind them means they'll be able to withstand Hizbullah's initial assault and early successes. Lines will be drawn, and it'll be stalemate. Whether Hizbullah is defeated will depend on multiple factors. Can Iran sustain the war effort for years with no end in sight? Will Russia support Hizbullah? Will Israel and/or Arabs get militarily involved?
But until that happens, Hizbullah will continue to dominate Lebanon's politics and will be the sole decision maker. They are much stronger in that regard than they were 10 years ago. It was to be expected, courtesy of Aoun and his party.