Why was Judas able to betray Jesus in the garden?
Judas was able to betray Jesus in the garden because Satan entered into him at a crucial moment, turning him into an instrument of Satan. From that indwelling, he acted under Satan's power, which enabled the betrayal. Later he tried to resist that power.
Les teaches that Judas was able to betray Jesus because Satan indwelt him at a crucial moment, just as Satan will indwell the man Antichrist at the midpoint. From that moment on, Judas became an instrument of Satan. That is why he was able to betray Him in the Garden. Later, when Judas tried to resist the power of Satan and threw the silver at the feet of the priests at the temple, something happened. Les says he will explain that more in detail from the book of John if time allows before going to Acts. He also notes the language can seem confusing.