What did Jesus mean when He said, “The publicans and the harlots go into the Kingdom of God before you?”Matthew 21:31

ESV – 31 Which of the two did the will of his father?” They said, “The first.” Jesus said to them, “Truly, I say to you, the tax collectors and the prostitutes go into the kingdom of God before you.

The context in Matt 21 is about their “nature” and Jesus can see through their “hearts”. The key difference between them and the chief priests and Pharisees are found in the examples and comments Jesus gave:
1. Repentance= Matt:21:29 “He answered… I will not: but afterward he repented, and went”. See also v-32.
2. Belief = Matt.21:32 “For John came unto you in the way of righteousness, and ye believed him not: but the publicans and the harlots believed him:” 
3. Fruits= Matt:21:43 “..,the fruits thereof.”
They “will go before them” because Jesus knew that it will be “easier” for publicans and harlots to believe, repent and express good “fruits” than the chief priests and Pharisees who even “sought to lay hands on him” (Matt 21:45-46).
It is about “timetable” for salvation. Each one at their own time already known to God.