Why was the conquest of england documented in a tapestry?

It was the Bayeaux Tapestry.  It depicted the Battle of Hastings were the Norman army led by Duke William also known as William the Conqueror fought the British Saxon army led by King Harold.  It depicted the battle from its preparations to the end of the war where Harold was killed and William was the victor.

there is not really a certain expensive film type but i believe all of them cost mostly the same price, i hope this a little bit