I could ask the same to you. If you could download CIAs from the eShop EVRRY CIA would be a legit CIA. You literally just said you don't know and never tried. The download will fail at 99% because there's no ticket on the NAND that dictates that you physically bought the game FROM the eShop.do you know why they are failing at 99%?
because the key to decrypt the contents is incorrect in the tickets/cia you installed.
because you are using 'bad' cias, cias not made with my tool FunkyCIA, or newer gui versions like GroovyCIA/CoffeCIA
cias made using these tools are good because the contents are never decrypted, we rely on the deccryption key in the ticket, not predecrypted contents like other cia creation techniques.
don't say you cannot unless you really understand what is going on!