What are the reasons for the victory of the army of parliament over the army of the king?

The Army of Parliament was made up of volunteers. We can say that this was an army of a new type, which was the main reason for the victory over the king. So by 1649, the English king was completely defeated and executed. Thus, the parliament was able to achieve its victory in this difficult war, where the struggle was between the old feudal and the new world. Despite this, it took several more years to suppress the centers of unrest in the country.