Read Pilgrimage to Hell again - Trader was an asshole before he left; he just became even more of one after he returned. It was noted several times that he was different - shorter temper, mood swings, short attention span, memory loss... Trader and Ryan knocking heads was bound to happen - in his day, Trader was the king and Ryan was his right hand. After Trader returned, Ryan was running the show, and Trader was still used to being the guy in charge, so it led to conflicts (and also because both men are strong-willed and unwilling to back down when challenged - it's necessary for a leader-type in DL). In the end, Trader did the honorable thing - he sacrificed himself to hold off the muties and brushwooders so Ryan and the others could get away (see the Shadowfall summary on the wiki).
Trader was a larger-than-life figure, a Deathlands legend, and the one who's largely responsible for Deathlands being what it is today* ("today" being "at the present time in the books
), as well as Ryan being who he is, but he's not the axis of the series... more like the foundation on which it's built.
*Not my opinion; this was noted in one of the books. It is arguably true, though... he supplied arms and equipment to villes looking to rebuild, fought against muties/bandits/warlords, helped propagate news and trade, and gave people hope. There are lots of times when the companions run into people who say "Hey, you ran with Trader? He did
for us, and we're so grateful!"