Its a good shot for sure, people saying otherwise are blowing smoke. Someone with practice or training could make that shot without much issue, but also remember that this was an extremely high profile assassination in front of a huge crowd during broad daylight against the ally of the most powerful and vindictive man in the world. Whoever did this not only had familiarity with firearms (was absolutely not a rando who made a sudden decision to buy a firearm and commit violence on a whim) but was able to keep their cool in a high stakes, high adrenaline situation. Im not saying professional hitman or agency operative, necessarily. But also definitely not your typical idea of an upset liberal soy boy who thought theyd give the 2nd amendment a try as an emotional response. This person knew what they were doing and had intermediately developed skills at minimum.