The mission was already fucked. The leak in their propellant system meant they couldn't achieve a stable orientation towards the sun. When the decision was made they had enough fuel to maintain attitude control for 40 hours, after which it would tumble and eventually lose power.

Deorbit while they could still command where the deorbit would occur was the only responsible choice.

The decision to deorbit was because of uncertainties around their already compromised fuel system.

The only responsible choice was to deorbit while they still definitely had the ability to control that deorbit.

The decision to deorbit was because of uncertainties around their already compromised fuel system.

Since they don't know how much delta V they have left, the only responsible choice is to deorbit while they still definitely have the ability to control that deorbit.