Re: Well that was an interesting turn of events!
To the OP: I have a feeling that was the GM's first experience of GMing (probably even of playing) online. That method of doing combat may work OK FTF, but by the time you finish even one round online most are bored, and the rest will be by the time you've done the whole combat and it's three months later.
I've ended up with GMing games where the original GM couldn't, for whatever reason, carry on, but no one has ever just dumped it on me without asking, without me being a coGM, etc. I think I'd have to be really invested, else I'd just post to all the players what had happened and delete the game. It's not the sort of thing RPoL can really make rules against, but it's rude IMO, and not very practical. Some allowance to be made of course, if the original GM has some life altering, unexpected happening, but even then if s/he/it can get online to change you to GM, surely there could also be a post giving at least a minimal explanation.