This is a very good question I've been asked repeatedly, so I'll answer below:
The Syrian rebels in the Fath al-Mubin ops command were probably assessing Hezbollah and allied Shia militias' capabilities. Hezbollah had every opportunity to show how powerful it was against a determined and powerful foe like Israel, but instead they got absolutely mauled in a matter of months (if we count the pre-Lebanon invasion clandestine ops like pagers blowing Hezbollah members' members off).
Launching "Deterrence of Aggression" now means Hezbollah remnants will have an extremely short time to reconstitute forces. They will also be still reeling from the devastating effect of Israeli power against their morale, the fact their leadership was assassinated with no response from Iran or anyone else, and their new leadership meekly reneging on their promise and bravado of never accepting a ceasefire unless a simultaneous ceasefire occurred in Gaza.
Also, compare and contrast Israel's success in Lebanon versus its abject failure in Gaza - they left Hezbollah in utter tatters in a little over a month, and have failed to end Hamas/Qassam in over a year of brutal combat and genocide. This is instructive on its own merits.