It always made me sad that, despite being so much like Goku in appearance and personality, all Goten knew about Goku for the first seven years of his life was what he learned from stories. Most of which he had been told by his brother. And, because of Gohan’s stories, Goten had the image of this great hero, of this angel that could always, no matter what, swoop in and save the day. That he could do anything. That dads could do anything and could do no wrong. That no one could defeat them - which is an odd perception for him to have, when you think of the fact that Goku was dead. Goku had died, so of course he couldn’t be the strongest (and, even if he was, he would still have faults, still couldn’t possibly do everything). Of course he couldn’t always be there to save the day. Of course he wasn’t perfect. Dads aren’t perfect - they aren’t angels like Gohan had him believe.
And Goten learns that the hard way. Because Goten, even though he didn’t know Goku, believed in him. Believed that he was the best. Because Gohan told him that he was. But Gohan died. And Goku didn’t save him. Gohan was Goku’s son and he should have been there to save him. But he wasn’t. So Goten’s image of his father is completely shattered, his trust in him is broken in the few hours that he’s known him by the time this scene rolls around. And - even though Goten gets that faith back when he finally sees Goku in action - this scene break my heart because Goten, up to this point, was always, always believing in him. So he can’t at all understand how Goku could let him down.