My take on this is that they probably were insolvent for a long time already due to previous hacks/theft. The CEO just decided to lie about the supposedly 137M in funds 'safely' stored on his laptop. This is also what happened at MtGox, except that at MtGox they 'lost' wel over a million BTC. Edit: relevant listening: https://darknetdiaries.com/episode/9/
> at MtGox they 'lost' wel over a million BTC. The initial report was 850 000 lost BTC which later was brought down to 650 000. Scroll to the end of https://www.mtgox.com/img/pdf/20140320-btc-announce.pdf
Apparently Karpeles also found a 'forgotten' wallet of 200k BTC, which he still seems to own. It's a mess.