Jesus chose Judas to be an apostle. Apparently, Judas was taught the same things as the other apostles and had the same types of experiences. It seems likely that Jesus loved Judas and valued him as much as any of the other apostles, at least until near the end.
Luke never met Judas. What Luke knew of Judas likely came from the testimony of the other apostles and from the stories he heard. We don’t read much about Judas before his betrayal of Jesus. It’s easy to suppose the Gospel writers so detested his betrayal that they were not interested in saying anything nice about him, but they also say very little about half of the apostles, so it may be that Judas was just like those apostles.
We are not told in the Bible when Judas started drifting away from Jesus. Perhaps he expected Jesus to overthrow Rome to establish an earthly kingdom and was disappointed when Jesus made it clear his kingdom was spiritual. Or perhaps it happened when Jesus called for his disciples to be fully committed and Judas realized he did not want that. Or perhaps it was some difficult teaching of Jesus or a time Judas was embarrassed by Jesus’ words or actions. We don’t know why or when, but we do know that the actions of Judas helped result in the death of Jesus.