You need a cheat so as to remove the security from the server* -- while it was all pulled apart such that we now know how it works we did not get any security certificates that the DS/game expects. Obviously a flash cart can also do a modified game.
*basically when it looks up
https://someurl.sometld you change it to
http://someurl.sometld. Not all programs/services work this way, indeed it is very bad form that it does and anybody that writes code like that for me will probably be fired on the spot. As removing things in a cheat is tricky then the cheats just take the characters and overwrite everything just like it would be if if the delete button was pressed and have a blank at the end to maintain overall size.
There is a way to run DS games on the 3ds these days, though it is slightly annoying to use
https://gbatemp.net/threads/ds-i-3ds-dsimenu-ds-i-menu-replacement.472200/ has more. A flash cart is still a better method and likely will be for some time to come. If you have a custom firmware one then you can also dodge a lot of the blocks and thus use a far cheaper flash cart than if you wanted ones for an otherwise unhacked 3ds.