Those stills make the first one even worse than it is. The AR would barely have been able to see the scorer, far less judge him offside.
The second one, total guess by me here but, the AR correctly waited to see what happened, as the ball went between the two blue attackers, its possible the AR lost track in his mind which one of the two were offside. ( a clip of it might explain my point better)
Harsh lesson for us all as referees, we can have a real decent game but some things are out of your control.