My guess is that the reason the Lebanese did not replace Hezbollah with Lebanese soldiers is either they didn't have the capability or perhaps they didn't have the will. Don't forget, Hezbollah is part of the Lebanese government and is very popular with the people. What are they supposed to do, go against the will of the people? Even if they did, would they be capable of doing that? I somehow doubt it.

Lets not forget that most Muslims in Lebanon see Hezbollah as their only protection against U.S. and Israeli aggression. If they didn't have Hezbollah and if the Palestinians didn't have Hamas, who would protect the people? Who would stop the aggression? If I were in their shoes, my attitude would be, better the devil you know than the devil you don't.