Polgara and Belgarath are both several thousands of years old, so I really didn't read them as smug or arrogant, rather jaded and cynical. Beldin was jaded and cynical personified.
I'm in my mid-50's and honestly can identify with them at times, although I do my best not to act it.
Garion's treatment is probably evidence of the Eddings' proclivities toward children. They were both convicted of child abuse and spent time in prison for it about 10 years before "The Belgariad" was written. Their adopted children were also permanently taken away. Like many others I had no idea of that until after David's death in 2009.
I reread it about 8 years ago and I've had both my boys read it as well. It certainly did hit a lot differently. For one, if I was Garion I would have sent Ce'Nedra permanently packing in short order destiny be damned. I still loved Prince Kheldar (Silk) though.
There have been so many authors and celebrities whose work I have enjoyed over the years just to come out and be scummy trash that I'm at the point I just want to enjoy the art and not know who is behind it. That feels a lot like being a ostrich with its head buried in the sand, but I'm not really sure what the alternative really is.