Chewbacca was a midget amongst Wookiees and and after two centuries of put downs over his relative diminutive stature entered into self imposed exile.
Never an intellectual giant (he was known for pulling the limbs of droids for besting him at computer games) he made the mistake however of teaming up with Han Solo.
While physically shorter, his ego once again made Chewie feel insecure.
After Han gained a medal for bravery from the Rebels and he did not, his cries of "I've had enough of this shit!" were drowned out by applause.
It is therefore no surprise he would immigrate to Endor where he would be seen not only as a physical giant but also as something of a hero.
Endorian females were very keen to get their paws on a bit of Wookiee Nookie and very few Ewok males were equipped to offer much in the way of competition (Zach Galifianakis being a notable exception).