Congrats on the crossfire. And yes.. it's always electrical. You were fine > replaced the battery > new battery drained (odd) > no start.
I know this may sound lame but it really does fix quite a lot of quirky but serious issues -- pull / check and reseat your fuses (like all of them).
This car demands a 100% working battery or the car 'will go funny'. double check your battery ground cable to frame - clean it.