In this video of the attack: https://twitter.com/MahirZeynalov/status/865301089867923456
a bodyguard is seen talking to someone in the back of a car. That bodyguard nods to another bodyguard, who then walks towards the protest. The attack begins the second he arrives at the line.
Later, the person in the back of the car gets out. It's Erdogan.
This video didn't get as much press as it should have, I suppose since you can't say it's "proof" he ordered the attack. But come on.