Oh, please.
This was literally the most targeted attack in the history of attacks. Small explosion on a personal device, worn by terrorists.
Go back to Iran.
...and there it is. Your bias is showing. According to you, all Iranians are terrorists.
Worn only by terrorists? You're sure of that? You might be willing to risk the same happening to you when a device held by someone standing next to you discharges, but others have rights not to be force to assume that risk.
And it's not the size of the explosion, it's that the targeters didn't ensure that the devices were only held by terrorists and that any innocents near them would be out of harm's way.