Why does Japan like turning things like war tanks, ships, historical figures or even fictional ones into anime girls?
Because they're cuter?
2D>3D
>>158920757
70% mythological history, 5% people tapping into a concept they think is underserved, 25% marketing.
Having an understanding of tsukumogami and the transformative nature of many other creatures from Japanese folklore makes the foundation for these cutesy transformations more "logical." But it's also that cute girls sell stuff and the creators of those types of things tend to be otaku for something unrelated to anime (guns/machinery/etc.) and choose to express that love in this way.