@Acsisnarf What kind of logic is it to choose a high school boy in the hero summoning ceremony of the cliche isekai stories?
It's a writer's choice. It's to make the MC look as close to the target reader audience as possible. It's so that the intended reader will feel a connection with the main character. In other words, it's self-insertion. There's a reason that the MC is the black-haired, introverted, bitter boy and not his white-haired, extroverted, joyful brother. It's self-insertion.
Separately, why didn't the buddha actually explain anything to the people until just now? You'd think that the buddha might actually tell the person hey, you're going to go to a future where certain things are happening, but I want you to keep certain other things in mind. It's a massive plot hole that you'd think he would at least try out given that he wants to change the future.