This may or may not be a great scholarly approach, although it does rely on the testimony of scripture. I believe it is true enough tonbear merit, however, and, consideringnit is upon the reliance of the text at its core, it is worthy of consideration. Albeit, it is, as well, from personal experience and observation, and is therefore the subject of my "informed" opinion.
I have come to understand this subject that Christ did not, at first anyway, even entrust his heart even to Hus own apostles. And, the reasoning is this.
Christ was, alone, the only man anointed with the Spirit. What He did, He had to do alone. Something we will never have to do. But, even speaking of His twelve, it is mentioned that He knew which of them believed and which did not.
It was not until real faith began to blossom that Christ called them friends. They had been servants, and Jesus specifically marks the transition to calling them friends. Elsewhere, before the cross, He said that He would in a short time no longer talk in parables, but He would speak plainly. At this, Phillip exclaimed, now you are speaking plainly, to which, Jesus said, At last you believe. Jesus had sais only He would speak plainly, not that He was then. What changed, then, was Phillips heart, into faith.
What is in view here, then, is the power of relationship over a soul. Just as someone with as much wisdom as Solomon could be led away by many wives, so close friendships, where there is deep koinonia, fellowship, act as a direct connection between one person and another.
While it is not much taught or talked about these days, Paul was fairly explicit about church discipline. Expel an immoral brother. With someone whoncalls himself a brother who is coveteous or idolatrous or sexually impure, do not fellowship or even eat. Warn a divisive person once, then twice, and then have nothing to do with him--he is depraved. The "leaven" of their lives will quickly corrupt you, and cause you distress.
So, the passage says that Jesus is quite aware of the contents of each person's heart. This includes the apostles. The amount of pressure does not have to be great, but if consistent over time, it can yield tremendous results. This is the issue.
Christ guarded His heart, because He knew, as He taught in the end of Luke 14, if you want to win a war against 40,000 with only 20,000, you have to not hold anything back (the final summary of His parables here). So, He is aware that impure relationships, or relations that have involved in them impure motives, will always tend to lead one astray in difficult times.
This of course may go against some teaching, such as the fact that the New Testament in no way calls Christ a friend of sinners. He was accused of that by the Pharisees, along with being a glutton and drunkard. He stopped for one short tax collector in a tree while passing crowds of thousands. He preached to one woman at a well, while leaving crowds at times. He was not primarily a 'friend to sinners', but a 'Great Physician' among patients.
Jesus was a man on an assignment, and it is the job of any good soldier not to become entangled in civilian affairs. He did not trust Himself, be friends with, be open and direct about anything, or let anyone in, with anyone, except the disciples and then, only as they began to learn and understand the Kingdom.