Fixing this brick
The following diagram may be of use when fixing WiFi bricks.
The Wii mini Hacking Discord server has recently began writing guides on hardware modifications for the Wii mini, and will likely write a guide for a WiFi module soon.
Cause of this brick
On boot, IOS pings the WiFi module to connect to the internet. If the WiFi module is broken or absent, IOS will hang as it receives no response.
Because the Wii Mini does not have a WiFi module, its IOSes do not have this code. However, if a normal IOS is installed, that IOS will hang when it tries to ping the non-existent WiFi module. If this IOS is IOS80, then it becomes impossible to load anything due to the System Menu never loading.