Why will my wii read a game disc, but a wii u will?

Why will my wii read a game disc, but a wii u will?

I recently bought a used copy of smash bros brawl, when I put it in my wii, it says it cannot read it. All my other games work just fine and the brawl disc was in good condition I tried putting the disc in my brother’s wii u, and it worked! I have been hacking the wii using the sd card, so maybe thats the problem? No idea, please help.