Looking at the assassination of First Lady Yuk Young-soo, wasn't the presidential security at that time the absolute worst?

I mean, how did the sniper manage to bring a gun into the event venue so easily?
And when the sniper was charging with the gun, the priority for the security detail should have been to shield the President and the First Lady with their own bodies, but no one stepped up to protect them.
Even Park Jong-gyu, a marksman who was the chairman of the shooting association, rushed out only to drop his gun while aiming at the sniper. Seriously...
How could the presidential security skills be that bad?
And his successor, Cha Ji-chul, wasn't even wearing a gun while eating next to the President, and instead of protecting the President, he ran to the restroom next to him lol
The Secret Service during the Reagan assassination attempt was top-tier, though.