Final answer:
King Henry VIII declared himself head of the Church of England primarily to gain control over the church and its wealth.
Step-by-step explanation:
The primary reason why King Henry VIII of England declared himself head of the Church of England was to gain control over the church and its wealth. While seeking an annulment to his marriage with Catherine of Aragon, Henry VIII wanted to separate England from the Roman Catholic Church.
By making himself the head of the Church of England, he could assert his authority over the church and confiscate the wealth of the monasteries to build his treasury.