Quite right. It's potentially an dereliction of duty and could be seen as being dumb enough that shareholders in a company could force an officer out (of course, here it doesn't matter b/c the company is bankrupt), but unless you can prove malice or untoward gains (like, the person making the Facebook buys was getting a cut from Facebook or money was being funneled from the ad buys into someone else's pockets, which does NOT appear to be the case here), there is no fraud.

When a company is going bankrupt, the best that can be done is that the backers can try to fight to be higher on the creditor list to get whatever scraps are left (assuming any scraps exist at all).