Point of view of this poem is:
1. ancient "russian Bulgars" lived in this area
2. then Golden Horde conquered them and built Kazan (modern historians say that Volga Bulgaria State built Kazan and Horde developed it to big city)
3. then Russia freed territory from Golden Horde
That is why author says "Kazan asked help".
For example wiki says 8000 russian slaves were freed in Kazan after Russia conquered.
However it's political question. You can note that author of 17 century is not very political correct for example in describing alien religion.![]()