(Typing while Ken posted....)
First thought is you got a bad battery that failed internally to ground, but if you've confirmed it to be good then I'd wonder, stock wiring or aftermarket harness? Just wondering if perhaps a fusible link to the fuse block gave up, or a Maxi-Fuse feeding the fuse block? Maybe check voltage at the battery, then go to your fuse block and check for power at the little test ports on the top of the fuses? Also check continuity on both + & - battery cables for grins?