Judas played such a key role in the death of Jesus. The enemies of Jesus wanted to end his career but they had no instrument to do it with . . . till Judas came along. I wonder how happy they were when he came for a visit? How they must have considered it good fortune. Probably they even thanked God for him.
Yet the eerie truth is given in the preceding verses that Judas was not led by God but Satan. The phrase "Then Satan entered Judas" seems to imply that Judas dropped all defenses, all pretenses and surrendered to Satan. Something changed that opened a pathway to his soul.
Was it a lack of focus on Judas' part? A lack of effort? Was it a turning to evil prompted by greed, or prestige or bitterness? So little is written but so much came from it. One person gave Satan entrance and everyone suffered.