He was going to use Wookies, but then they pointed out he needed more characters to sell toys, and they came up with Ewoks, so they could sell toys and lunchboxes and videos and stuff. They had the Ewoks there for the commercial factor only.

Now... wouldn't be great if one of the Jedis killed on Order 66 was killed while on the moon of Endor, and then an Ewok would approach the dead Jedi, and try to wake it up, and realizing it is dead it would bend over and sort of cry/pray over that dead body?