Need to do a bit of history Pluralus.
Hezbollah arrived on the scene in 1982.
A civil war had been raging long before.
Most historians see this as the main cause:
"There is agreement among historians that the war broke out as a result of a period of growing division between those Lebanese who supported the right of the Palestinian resistance to stage operations against Israel from Lebanese soil, and those who opposed it."
Lebanon's Christian minority, the Maronites, who do not see themselves as Arabs, also played a role ( 21% of the population),
They re-organized their militia, called the Phalangists, who were supported by, you guessed it, Israel.
From Britannica:
"Israel's Maronite Christian allies, the Phalange Party, contrary to General Sharon's expectations, did not act to secure the city as they had been expected to do."
Don't forget the two massacres carried out in Beirut's Palestinian refugee camps, Shatila and Sabra.
"Israel's occupying army was in full control of Sabra and Shatila, and sent the Phalangist fighters into the camp knowing full well their hatred of the PLO and history of atrocities against Palestinian civilians.
"In particular, Defense Minister Sharon bore responsibility for the massacre."
Explainer: The Sabra & Shatila Massacre - IMEU
Institute for Middle East Understanding (IMEU)
https://imeu.org › article › the-sabra-shatila-massacre
The number of civilians slaughtered, you might inquire?
"...at least 1,300 named victims and estimated a maximum of 3,500 people were killed."
Back to the main:
Palestinian refugees, who legally deserved a right to return, and had been denied, despite international law, were attacking Israel from the South.
"In response to Palestinian attacks from Lebanon, Israel invaded in 1978 and again in 1982. "
"Hezbollah was established by Lebanese clerics primarily to fight the 1982 Israeli invasion of Lebanon.
"It adopted the model set out by Ayatollah Ruhollah Khomeini after the Iranian Revolution in 1979. Since then, close ties have developed between Iran and Hezbollah."
"After this Israel occupied southern Lebanon until 2000, while fighting a guerrilla conflict against Shia paramilitaries."
"After Israel's withdrawal, Hezbollah attacks sparked the 2006 Lebanon War."
Here's a convenient timeline:
Timeline of the Lebanese Civil War From 1975-1990
ThoughtCo
https://www.thoughtco.com › Issues › The Middle East
Aug 12, 2019 — The Lebanese Civil War took place from 1975 to 1990 and claimed the lives of some 200,000 people, which left Lebanon in ruins.
BTW: Currently around 270,000 Palestinians living in Lebanon.
Lastly, I hope this helps dispel some of the myths used to justify Israeli transgressions, their goal to ethnically cleanse more and more Palestinians from 'Greater Israel', and keep their neighbours in a constant state of war, or threat thereof, always against each other.