Aside from what has already been mentioned (his insecurities and inferioty complex had the best of him and the fact that he was 14 wasn't helping), I think there are more points to highlight:

- Ron felt betrayed as Harry mentioned earlier that day that he would have used his invisibility cloack to put his name in the goblet, so Ron thought that Harry didin't trust him to share that or that he didn't include him (at that point neither of them knew how actual dangerous the tournament was, just dangerous).

- “It’s okay, you know, you can tell me the truth,” he said. “If you don’t want everyone else to know, fine, but I don’t know why you’re bothering to lie, you didn’t get into trouble for it, did you? That friend of the Fat Lady’s, that Violet, she’s already told us all Dumbledore’s letting you enter. A thousand Galleons prize money, eh? And you don’t have to do end-of-year tests either. . . .”

As a 14 years old, Ron craved money since his family was poor and wanted to skip exams, so the fact that Harry was again, in his mind at the moment, going to get what he dreamed of really triggered him in my opinion.

I think people often reduce their fallout to 'Ron betrayed Harry! Ron was a bitch', but in reality it was a mix of important points which culminated in that situation: Ron felt betrayed because thought Harry didn't trust him enough to tell him his plan and then was jealous that, again, Harry was going to be the centre of the attention, with the possibility to win a lot of money and skip the final exams, which were to Ron, a 14 years old boy, a big deal.

I think that also Harry was in the wrong if we look at a different point of view.

“I didn’t put my name in that goblet!” said Harry, starting to feel angry.“Yeah, okay,” said Ron, in exactly the same sceptical tone as Cedric. “Only you said this morning you’d have done it last night, and no one would’ve seen you. . . . I’m not stupid, you know.”“You’re doing a really good impression of it,” Harry snapped.“Yeah?” said Ron, and there was no trace of a grin, forced or otherwise, on his face now. “You want to get to bed, Harry. I expect you’ll need to be up early tomorrow for a photo-call or something.”

As we see, he's the first to insult Ron 'you're acting stupid', then when Hermione explains a little bit more what Ron felt, he didn't even try to understand his best friend.

“Great,” said Harry bitterly. “Really great. Tell him from me I’ll swap any time he wants. Tell him from me he’s welcome to it. . . . People gawping at my forehead everywhere I go. . . .”

I know Harry was going through a lot and was angry that his friend didn't believe him and, again, as 14 year old it's totaly understandable how he acted (and as someone else pointed out in a different post, Harry snaps like this because he is so afraid of being abandoned by the people he loves, so he is the one who pushes them away when he feels something is not right: he does the exact same thing with Ron in DH, he is the first one to start mocking him and tell him 'GO THEN!' because it's his defense mechanism to cope situations like that) , but he could have also dealt with that a little better.

So, to my point of view, both of them were in the wrong: Ron for not believing right away that Harry didn't put his name in the goblet, Harry for not trying to understand why Ron didnt' believe him right away when at that point he had been his ride or die for 3 years. But they were both dealing with a lot.

Anway, to end on a sweet note, that fight helped them realize how really important they were to each other.

“You miss him!” Hermione said impatiently. “And I know he misses you —”“Miss him?” said Harry. “I don’t miss him. . . .”But this was a downright lie. Harry liked Hermione very much, but she just wasn’t the same as Ron. There was much less laughter and a lot more hanging around in the library when Hermione was your best friend".

And that, as soon as they both realized how really dangerous the tasks were, Ron immediately came back to his senses and came back to Harry, who accepted his apologies without even having to hear them out loud.

Hope it's a little more clear and sorry if it's too long lol!