Israel occupied Lebanon in 1982. Hezbollah was formed in response to the occupation. So Israel directly created Hezbollah. Iran-Syria-Lebanon have a mutual defence interest in banding together to fight Israeli aggression. I am impressed by your mention of Ma'alot, which was an atrocity, but also impressed of your lack of concern for Israeli atrocities (white phosphorous, cast lead, Sabra and Shatilla massacre (for which the Kahan commission blamed Arik Sharon, Jenin, Gaza etc).
U.S. confirms ISIS computer expert killed in air strike (Reuters)
from the article: U.S. warns Syria: Stop arming Hezbollah immediately