Energy retailing is, AFAICS, a very low fixed cost business. You don't need to own any expensive infrastructure. You just buy electricity from the wholesale market (usually time-varying, although careful operators can of course hedge their positions), and sell at fixed price to consumers. You essentially need a web site and a bunch of annoying telemarketers.

It seems what has happened is that many of these retailers are some small fly-by-night operations. When wholesale prices are low, they make a lot of hay (making sure to store that somewhere that regulators can't get their hands on them), when the wholesale price rises, well, declare bankruptcy, and start a new company doing the same. Rinse and repeat.

Regulators should really step up the game, making sure that retailers are properly hedged etc. Or then forget this idea of "deregulated" electricity markets.