What brought Iranian forces to Idlib front?

The other item may well be that the Syrian forces are unable to concentrate enough force to fight the battle - being they are spread thin by taking areas and having to hold them. But concern with the Iranians might also be there in the background as well. A failure by the Iranian allied forces committed to the fight could be strategically deadly.

The Shia helps Russia help the Syrian army in this religious civil war.
The Sunni rebel forces supported by Turkey and Saudi Arabria started this crap. We use to arm both sides.
Now, for some reason, we interfered with the Sunni Caliphate (ISIS), in favor of supporting the gloabal approved Sunni Caliph in Turkey. The Syrian Sunni rebels will possibly get a section of northern Syrian land which Turkey can help defend in return for loyalty.
In Libya, the county destroyed by NATO, has Sunni fighting Sunni. In one corner is Turkish supported war lords. The other, ISIS types. Egypt just entered into the issue in Libya.
What a religious/politiacl cluster ***k SFC.

Over compensated for Soleimani's death - Qaani is responsible for recruiting the Liwa Fatemiyoun and Liwa Zainebiyoun in Syria so I'm not surprised his first agenda is to establish his influence in Syria.