Why when I upload the new item with new hierarchy the previous one got deleted?

Hi experts ,

Why when we upload new item with new hierarchy structure, the previous one got deleted ?

We have :

Product family (level 4) - product category 1 - product category 2 - sub category - Item (level 0)

our existing hierarchy :

Shoes - Flat Shoes - Sneakers - Sneakers regular - Item XX,Item XY, etc..

we want to add a new hierarchy for new product, so I uploaded :

Shoes - Flat shoes - Sandals - Sandals regular - Item YY

but what happen after we run the demand planning, from the selector tool we have this category only :

Shoes - Flat shoes - Sandals - Sandals regular - ITEM XX, ITEM YY