Curate, connect, and discover
Mezato is a very intriguing person despite her position as a side character restricting the audience's knowledge on her, but there are some implications I have become very interested on.
During her conversation with Ritsu post-LOL Cult arc, she mentions something akin to "people really aren't born as equals", referring to how Mob is so disadvantaged compared to Ritsu even thought they're siblings. However, that also says a lot about her motivations. Mezato has two main reasons for organizing the Psycho Helmet Cult and trying to make it influent (with Mob's help as their messiah): 1) it sounded fun; and 2) she wanted to take part in such a massive event. Although the "fun" part can be attributed to the fact that well, she is a fourteen year old with a weird perspective, both motivations are directly associated to not only Mezato's passion, but her opinion on herself.
First of all, she becomes fixated on anything that appears worthy of her attention. It kickstarts her adventures as the school journalist, hunting for any kind of news that she believes to be interesting, and by that she doesn't mean "math class is cancelled": Mezato goes far beyond, from catching shoplifters red-handed to infiltrating a cult that supposedly brainwashes its members. It's clear that the mundane is not enough to her. Mezato wants the current biggest thing. This is one of the reasons she gets so interested in Mob, and being so obsessed with the worldchanging, Mezato cannot bring herself to care as much about the common, the mundane. This way, she can only see entertainment, or better put, value, in what stands out.
Equally, Mezato wants to participate in something she sees as 'big'. Being someone who is so attracted to the flashiest parts of reality, she wants to have an active, direct role regarding them. It makes her feel entertained. It makes her feel fulfilled. It makes her feel special, most of all, because even being in the Biggest Thing's shadow removes her from the condition of banality she disdains so much. That's what makes the Psycho Helmet Cult sound like such an excelent idea, as hollow and uncritical it could be.
But what does these beliefs say about Mezato? Simple. Mezato doesn't think she can be interesting or valuable by herself. She is not shown as pretty, or academically gifted, or athletic. She doesn't appear to have friends. She doesn't even have an ability with the occult like Mob does. Mezato is a normal, lonely girl who has no other excuse to be noticed besides her imprudent detective work, but worse than that, she thinks she can't change. Mezato will never be attention-worthy as herself, so she appeals to inserting herself in whatever interesting thing she finds in the hope that it'll make her Someone by association. She could be a loser, a nobody, but at least she helped build something that is wonderful, and that is the closest she can get to being important.
Her interests and achievements, in this sense, are more like an extension of herself than a result of her passion. A passion that isn't understood by anyone else. A passion that others ignore and are annoyed at, which only reinforces her loneliness and her obsession with chasing after Big Things. If she succeeds, she will finally have a part of herself she can be proud of. After all, there are a hundred wonders in the world with the potential to change everything; there is only one Ichi Mezato and she can never be like them.