Chain of Memories GBA

Is there a specific reason why Chain of Memories was released on the GBA instead of the PS2? I'm talking when it initially released. I'm aware that Re Chain of Memories is the definative version on PS2, PS3, PS4, Xbox One, Steam, etc.

I'm talking like when it first released, why on the GBA & not on the PS2?

Isn't that also what caused confusion initially too? "Do I play Chain of Memories on the GBA or Kingdom Hearts 2 on the PS2 first?"