Why Kingdom??
Kingdom of God and of Heaven, is the realm (in heaven, on earth, under the earth), over which God reigns as king!
The kingdom of God means more than just being saved and going to heaven, although that is a major part of it.
It is the heart of Jesus' teachings, and means any situation on heaven or earth that reflects God's power, sovereignty, and holiness.
The ‘Treasury’ of this Kingdom--(called Insider Sources), refers to the rich resources within His Kingdom that is not readily available to the general public.
In Mark 4:11, Jesus replied to His very own disciples:
He said to them, “The mysteries of the Kingdom of God has been given to you (who have teachable hearts), but those who are outside (the unbelievers, the spiritually blind) get everything in parables.
It may seem unfair that the disciples receive the mysteries, where the others don't, but the parable of the sower explains why they have access to more information.
They are the "good soil." Those that readily accepts the seed of the Word, and nurtures it to germination, "yielding the measures” of thirtyfold, sixtyfold and a hundredfold" (Mark 4:8).
In other words, they are those, who choose to stay and ask for clarification. They are the people Jesus will describe in Mark 4:24–25 who bring the “large measure” because they want to understand things. They have access to more information.
They are the good soils that readily accepts the seed and nurtures it to germination, "yielding thirty-fold and sixty-fold and a hundred-fold." In other words, they choose to stay and ask for clarity.
Jesus says that the general crowd, receives His verbal teaching in parables. This includes why His physical miracles have a deeper meaning than what's seen on the surface.
All of Jesus' ministry is hidden from those who don't dig deeper
This doesn't make God's truth hidden, or mystical, or even complicated—it just requires that a person care enough to actually pay attention and be willing to learn, if they have the desire.
When He speaks in parables to the assembled crowd, he is actually giving them an opportunity to decide how much spiritual truth they want to absorb.
Jesus made a habit of explaining parables to those who wanted to know more than the general crowd. The fact that they are curious proves that they are the good soil that will produce much fruit.
Jesus further explains, how the growth of the seeds represent why people react differently to His messages. Always be aware that
A person's spiritual knowledge is based on their willingness to pursue deeper truth.