thats why they never mention the "administrator's" name. It could be G-Man, it could be someone else. And maybe the expieriment went wrong on purpose. When all of the eqipment was failing and the scientist team tryed to warn them and they didnt listen? Sounds like a government conspiracy to me.
I also think that the G-Man was working for The Nihilanth but he betrayed him and let him get killed by Freeman. G-Man had other plans. So when he saw you could get through it all, he wanted to use you to obliverate all of the alien race. Hence Half-Life 2.
What do you guys think of my opinion?