>why did Pikachu become the mascot?It's easy to forget because it was so long ago and everyone reading this likely isn't Japanese and at least in their late thirties, but there was a time when Pokemon was just a random new RPG released for the Game Boy that suddenly started ballooning in popularity. Pikachu wasn't made to be anything special, but its nature as a cute creature that can be found early in the game (but at the same time is relatively rare) and has a desirable, likewise slightly rare elemental typing was a suitable mix of qualities that made Pikachu naturally popular among players. And among the Pokemon that were popular with that early, growing crowd of fans, business people eventually decided that Pikachu was the best fit for a general face of the franchise. For a short time, the earliest Pocket Monsters manga had made Clefairy the de facto mascot, but it wasn't to last.
But hey, you guys don't have to take some random anon's speculation and stories for this, there's people with receipts out there backing them up, like Dogasu.
https://dogasu.bulbagarden.net/learn/rumor_guide/ash_starter_clefairy.html(Personally, the most interesting part here is that despite everything else, Dogasu can't actually find the oft-reported early CoroCoro Pokemon popularity contest. That would be interesting to see if it turned up anywhere.)
Anyway, while do I like Eevee, I don't have any special affection for it over any other Pokemon. And it would most likely be a much worse fit for the mascot for multiple reasons, like it not being nearly as striking in appearance as Pikachu is.
