Because belonging to the church (being a church official such as a priest or a bishop) esentially meant you were given education (not common or at all present in those times) and a good position with a pay. You also exerted a lot of power in your local or regional community as church officials were considered to have been influential figures in medieval ages.
If you want help, in the future be more specific and post the article and real question because most of us who want to help you aren't in you class. Just a little not for the future <3 Good luck in school!
Sincerely,
A Former Student