If you believe that domestic violence is a serious problem and that abusers must be held accountable, it is also possible to believe that Heard falsely accused Depp.
But, if you believe both those things, you are not celebrating or spiking the ball right now because even if you're grateful that a false accusation was exposed, you are horrified by it and understand what a setback it is.
It is a pyrrhic victory at best, not cause of cheering and high fives.
If you're happy about the result, as opposed to seeing it as necessary but horrible, I think you are happy precisely because it is a setback for MeToo.