@Nexelred @Psyramics
The story "explains" that with the MC having a lot of "useless" skills that combo well with each other and his luck stat being maxed out (see chapter 29 for luck stat info).
So for example the MC uses a skill (probably something like basic earth magic) to make that tube of earth.
Then he strengthens it with some other skill effects.
Finally he flattens those caterpillars with it while also having his luck stat take effect to deal increased / critical damage.
That is the "explanation" as far as I understand the story.
What is really not making sense is how his classmates - especially the class president - treat him as if he was weak (e.g. not wanting him to leave the town and to go fight monsters alone) just because his level is low even though they all know that he is far stronger than all of them combined.
That is the real stupidity in the story.