Imagine yourself that you're controlling a species in another dimension.
You were fighting with another species for long long time. Your enemy is cruel and mercyless, they won't stop utill they conquer everything you own.
You are about to lose, and you don't have many options. You have no chance to win.
Your knowledge of existing dimensions is big, and you have an experimental technology you can use to pass to another dimension. Your dimension is about to collapse, and you have very little chance to find life in another dimension. The enemy doesn't have this knowledge.
Your options are:
1. Let the enemy enjoy victory, untill you both die with the dimension.
2. Risk using experimental technology to evacuate to another dimension that might be empty.