I have killed all these three ruler after they started war against me in same war but whomever comes after still keeps 5k army without loosing its allies. Even the ruling family changed. I can't break this country. What is wrong with this, is this normal?

Crusader Kings is a historical grand strategy / RPG game series for PC, Mac, Linux, PlayStation 5 & Xbox Series X|S developed & published by Paradox Development Studio. Engage in courtly intrigue, dynastic struggles, and holy warfare in mediæval Europe, Africa, the Middle East, India, the steppes and Tibet. Can you achieve fame and fortune for your noble family, or will your names be forgotten to history?