If God Kalki has come then why it is secret?

Whenever God comes to earth in human form to establish religion, only a few devotees come to know about it.

These are the devotees who have been in the company of God in the establishment of religion in the previous eras in their previous births.

That is, only the devotees who are very close to God can understand the inconceivable Leela(Divine Play) of God by the grace of God himself.

No other person can know about God without strong devotion.

Because God cannot be known or understood by the senses. Devotion is the only way to know God.

Even in the Dwapar era, when Lord Shri Krishna was playing Leela with the cowherds in Vrindavan, even Brahma himself was unable to understand it, and even Indradev could not understand that Leela of God.

In this terrible Kaliyug, how can ordinary people understand God's Leela so easily?

To understand the divine play of God, dedication and selfless devotion are necessary. Even a small part of knowledge about God cannot be found through arguments.

Shrimad Bhagwat Mahapuran (1.1.20)
Lord Krishna used to hide himself and used to act as if he were a human being in front of people. But he has performed such divine plays with Balarama and has also displayed such valor that humans cannot perform.

Shrimad Bhagwat Mahapuran (1.3.29)
This story of the incarnations of God is extremely secret and mysterious. The person who regularly reads it with full concentration in the evening and morning with love gets rid of all sorrows.

Shrimad Bhagwat Mahapuran (1.3.35)
Truly, those who are knowledgeable describe the unnatural birth and actions of Lord Hari, the Lord of Hearts, as one who has neither birth nor actions. This is because His birth and actions are the most secret mysteries of the Vedas.

Shrimad Bhagwat Mahapuran (1.9.16)
No one knows what Shri Krishna wants to do and when. Even great scholars are fascinated by the desire to know this.

Shrimad Bhagwat Mahapuran (1.9.18-20)
This Shri Krishna is God himself. He is the root cause of all and he is supreme Narayan. Fascinating people with his Maya, he is playing hidden among the Yaduvanshis. 18.

His influence is extremely deep and mysterious. Yudhishthir! Only Lord Shankar, Devarshi Narad, and Lord Kapil himself know about it. 19.

The one whom you consider your cousin, dear friend, and the biggest well-wisher and whom you have not hesitated to make your minister, messenger, and charioteer out of love, is the Supreme Being himself. 20.

Shrimad Bhagwat Mahapuran (7.9.38)
Purushottam! In this way, you take the incarnation of a human, animal, bird, sage, fish, etc., and protect the world and kill the enemies of the world. Through these incarnations, you protect the religions of each era. In Kaliyug you remain hidden and secret, that is why one of your names is also 'Triyug'.