In an interview toriyama mentioned hating the anime for making goku too heroic, where as he always envisioned has having a little "poison" in his character. Looking over the series it's easy to see what toriyama meant.
>1) sparing Piccolo/vegeta just because he wanted a rematch
>2) lying to Roshi about not wanting to travel to namek when it was mentioned there was a higher power level on that planet, only because the old man raked him over the coals when he found out he spared vegeta
>3) playing dumb about the androids after his talk with trunks, endangering everyone after being told by a man who turned freeza into diced onions that said androids made two super saiyans look like complete chumps
4) putting everyone's lives in danger by tossing cell a senzu bean and telling gohan to fight him, when after an entire year of one-on-one training with the boy he failed to realize his son wasn't a natural fighter like he was*
5) half-assing his fight with fat buu just to see what fusion was capable of
6) refusing to save gohan (as well as Piccolo and the kids) when kid buu was detonating earth because he wanted to fight the wad of gum again and didn't want to watch gohan one-shot the imp
This is not the behavior of a mentally sound man, and childhood head trauma does not explain nor excuse any of this. I have to legitimately wonder if toriyama doesn't have some issues himself, as he's gone on record saying that goku is his favorite character to write. If the main character is an autistic man-child and the story arcs are fundamentally identical in pacing, tone, and fight outcome, what is the appeal in dragon ball outside of toonami-baby nostalgia?
* I will concede that the personality stapled to gohan during the cell saga is very forced, as the kid's entire character premise was being a nice lad with a monstrously explosive temper when his friends were being injured, but goku being a nigger-tier father still applies in that particular context