I don't think Iran are entirely blameless given their sponsorship of Hezbollah and participation in the Yemeni (and previously Lebanese!) civil wars. They've been maintaining a sort of sub-threshold threat in the area for a long time. Which was why, yes, it was an incredibly bad idea for US/Israeli attacks to escalate that.
https://arabcenterdc.org/resource/the-lebanese-civil-war-in-... (article is rather more favourable to them than I would be, but it describes the basic history)