as mentioned, the region has been mostly inhabited by shi'te colonists from syria for some time now, who have driven out the indigenous christian groups and invited hezbollah in to set up institutions. the lebanese government has been unable to prevent this.
it's hard to oppose the idea on it's face. israel should be rewarded with an increase in territory for the hardships it endured after oct 7, and the lack of support it received from the surrounding countries. the israelis are morally justified in expanding territory into lebanon, syria and gaza itself (if it really wants) on these grounds. and lebanon is both unable and unwilling to govern this area south of the river.
there needs to be consequences for failing to prevent terrorism from existing on your territory.
it's a reasonable outcome.