Why was Judas able to betray Jesus?
Judas was able to betray Jesus because Satan entered into him at a crucial moment; from that moment on, Judas became an instrument of Satan. This satanic indwelling empowered him to carry out the betrayal in the Garden. It was a pivotal moment, not merely human weakness.
Les explains that just as Satan indwells the man Antichrist at the midpoint, Satan also indwelled Judas at a crucial moment. Les asks his audience to reflect on when Satan indwelled Judas. From that moment Judas became an instrument of Satan, which is why he was able to betray Jesus in the Garden. Afterward, when Judas tried to resist the power of Satan and threw the silver at the feet of the priests at the temple, the language can seem confusing. Les notes he would explain more in John if time.