You don't mention Gaza or Palestinians, yet it's right there (and been there for 75+ years).
Hezbollah states that their aims include destroying Israel, instilling a Muslim government in the land, and converting the people to Islam.
They have explicitly said that they will never coexist peacefully.
Hezbollah's founders writings at the time are available online, and that they are clear about their goal being the rule of Islam. Their slogan was 'The Islamic Revolution in Lebanon'. They were founded as an Islamic revolutionary group, that is very core to who they are. Highlighting that is hardly 'using Islam as a scapegoat' whatever that means.
[1] https://en.wikipedia.org/wiki/Lebanese_Resistance_Brigades
You are trying to obfuscate Hezbollah's public statements calling for Islamic rule. Hezbollah wants Islamic rule and Sharia law for Lebanon, they are very clear about this. Currently realities that they have to put up with do not change that. They are also clear all of their actions and philosophy is consistent with and based on Islamic teaching. Again it is not deceptive to point out they are an Islamic organization.
> The 1982 Lebanon War began on 6 June 1982, when Israel invaded Lebanon. The invasion followed a series of attacks and counter-attacks between the Palestine Liberation Organization (PLO) operating in southern Lebanon and the Israeli military that had caused civilian casualties on both sides of the border.
You asked "but what pissed them off so much". Maybe it was the PLO operating in Lebanon, not sure.
Why, Israel sent them a page and they are merely returning the call, as would be the right thing to do among polite company.