My guess is that there certain vetos by the US, Turkey and Russia when it comes to invading Syrian government territory, so they’re targeting someone like Maher to signal that they’re on the side of the rebels and to try to embolden them into starting something to stop the current frozen state of the war. They want chaos on the Syrian government side and hope on the rebel side, so that some kind of shift can occur and make Syria useless as a transition point for supplies from Iran and Iraq into Lebanon
The invasion is officially on according to resistance media.