One thing we need to be cognizant of.
Iran’s redline for Israel was Beirut/Dahiya, not all of Lebanon (including southern Lebanon). There were plenty of attacks by Israel, and Israeli incursions into southern Lebanon, without eliciting a response from the Iranians.
Even Trump’s previous statement was about him asking Netanyahu not to attack Beirut.
So this might (or might not) be a mistake on Iran’s part. Maybe they feel confident that Hezbollah and their FPV drones can inflict serious damage on the Israelis and increase costs on them; so they don’t need to get directly involved.
I’m not so sure about that: while think Israel has incurred a big cost in southern Lebanon, Southern Lebanon (not Hezbollah necessarily) has incurred a far greater cost from Israeli attacks.
It will be humiliating for Israel to not directly attack Iran after this, but they can still keep the heat up (or expand) in southern Lebanon and not get the Iranians involved.