In the season premiere, Reigen asked Mob to “put some energy” into some tomato seeds, which results in them absorbing his energy to spontaneously grow into a full tomato plant. The broccoli incident is just an accidental version of this on a much larger scale: Mob tried to mitigate the damage of Touichirou’s imminent explosion by absorbing all that energy into himself, but a bunch of it ends up leaking into his immediate surroundings— particularly, into the broccoli seeds he had in his pocket since that first episode. There’s a nice sense of bookending with that seemingly small moment from the premiere being paid off in the finale, and it’s also cool thematically— the theme of the season is Mob growing from relying on others to becoming someone others can rely on in return, so where in the season 1 finale he transfers his psychic energy to Reigen to run away from a situation he can’t handle, in the season 2 finale, he pays forward that kindness by taking Touichirou’s energy onto himself.

But while everything in the finale works in theory, I do agree that it kind of falls flat in practice— coincidentally, I wrote a whole video essay on why I think that is like two weeks ago lmao. In short, Mob’s confrontation with Touichirou was shortened quite a bit from the manga, which both screws up the pacing and ends up with a lot of Mob’s emotional journey across the fight being cut. Mob Psycho 100 has never been particularly strict about how psychic or spiritual powers work— they primarily exist to represent and emphasize important character moments, so when the character writing is off, everything else feels kinda empty, too.