The thing is, it's in the title for what the MC is. He's not meant to be some Jesus-kun Isekai warrior that knows how to suddenly deal with every single high pressure situation properly or even really think before he acts on an impulse-he's a nobody goofball who reacts opposite of the Isekai hero trope, it's kinda the point of the story.
He acted on an impulse of anger from the shitty situation he's in and didn't think of the consequences. He's not and has never been a fighter, so grabbing a weapon and his things after hearing a Goblin bellow to alert the entire tribe isn't something someone who has never been in such dangerous situation, and with a mind racing at a 100mph would think to do; it's run and try to escape, or stay to loot and potentially get killed.
I do really appreciate you taking your time to play however. I do think you're taking what is meant to be a lighthearted, comedic segment and thinking about it too seriously, and more in tune with how an Isekai protagonist would usually behave, but there'll be plenty of serious moments throughout the story as he evolves as a character, so I hope you'll keep an eye on it for future updates.