“And he strictly ordered them not to make him known.” – Mark 3:12
As we read and study the book of Mark, we cannot help but notice that Jesus ordered individuals not to tell others about Jesus. In the beginning of His ministry, for example, he did not permit the demons to testify about Jesus even though they knew exactly who Jesus was (Mark 1:34; 3:12). Some say that this is because Jesus didn’t want demons to be among His witnesses. However, this was clearly not the case because Jesus also gave people the same order (Mark 1:44; 5:43; 8:30).
One of the reasons, I believe, was that Jesus knew that if many people knew who He was and what He could do, Jesus would not be able to move freely into towns to preach the Kingdom of God, which is the primary reason why He came (Mark 1:38). True enough, in Mark 1:45, Jesus could no longer openly enter a town because of his popularity.
However, I believe this was not the primary reason because interestingly, in Decapolis in Mark 5:19, Jesus actually said to a man healed from demon possession, “Go home to your friends and tell them how much the Lord has done for you, and how he has had mercy on you.” So, there must be yet another reason for this ‘secrecy.’