Could the glades not have paid Tribute to the Khazars?

Could the glades not have paid Tribute to the Khazars? Why did the conquered peoples who paid the tribute with arms cause fear among the conquerors?

In the 8-9 century, the tribes of the Polyans were under pressure from the Khazar Kaganate, in connection with which they were forced to pay tribute to him. Naturally, they could not pay tribute, but for this it was necessary to create a strong army in order to repulse such a powerful enemy as the Khazars.

The main reason for the fear of the conquerors was that the peoples who made weapons could raise an uprising, since they had the opportunity to create their own combat-ready army.