Russia must have given Turkey the green light, because Russia controls the airspace over Afrin. The reported deal to exchange Afrin for parts of Idlib would make sense.
Turkey will likely have a much harder time in Afrin than they have in the other parts of Syria that they have previously invaded and are occupying, because the Kurds are better fighters. They have demonstrated that they also have anti-tank missiles, and have been reported to now have anti-air missiles as well - so only high flying jets can operate, now attack helicopters. Turkey can afford to lose a lot more tanks than aircraft.
I saw another report that it was up to three tanks lost so far. That could go on every day, and snipers could be picking off individuals. It will likely be a steady flow of casualties while the Turks are in Afrin, but they can inflict significant damage to critical infrastructure like fuel storage, and then place an economic siege on the region.
those missiles and other weapons probably were shipped from Benghazi