The whole thing is well worth reading for anyone involved with VC funded startups. It involved an acquisition with a management incentive plan and preferences that together left nothing for common.

Among other things the court held that where there is a conflict of interest the board must prefer the interests of common shareholders over those specific to preferred (the interests of preferred over common being contractual). It also found that the board had acted procedurally unfairly and in several places suggested outright dishonesty. For those reasons it applied the harshest standard under Delaware law (entire fairness).

In the end however, it found that the company's value as an ongoing concern though not nothing, was not enough to overcome the large liquidation preference and cumulative dividend. Thus, since prior to the deal common stock was worthless a deal valuing them as worthless was fair within the meaning of Delaware law. Note that the litigation lasted 8 years, and at the end of the linked decision it was an open question whether the defendants were going to have to pay plaintiff's legal fees despite having won. (I couldn't find any information on what was ultimately decided there.)

The board decides whether or not to take an offer and that offer includes a set of destinations of funds. In particular, the offer may be $Z = $X1 for retention bonuses and $Y1 for purchasing the equity. Or, the offer may be $Z = $X2 for retention and $Y2 for purchasing the equity. The management - who are likely on the board - may want more of the money to go to retention bonuses for senior execs, while the external board members may want more of the money to go to shareholders. And, in many cases, a board member may be involved in negotiating the deal with the acquirer and may push for a particular deal structure.

tl;dr - The board can have significant impact on how the funds get split up, regardless of the previously signed contracts.