That's just it, 65 - 75% efficiency is still a lot better than having it wasted or end up on the market at negative value for power wasters like crypto farms and Facebook datacenters to just use up.
It's better for crypto farms and Facebook datacenters to use the energy instead, the efficiency is higher. If it would be wasted then it would be worse than this solution.
When you say something is "better" you are talking ideology, not physics. Why is crypto "better" than literally any other application which could use excess energy production? For example, carbon sequestration.
It's not that crypto is better, it's that using it directly is better from an efficiency point of view. If you used it for carbon sequestration that would also be better compared to converting it and retaining 65-75% of the energy before using it.
It all depends on what you would have used the 65-75% of it on, later. Used at 65% to displace carbon emission overnight would be overwhelmingly better than for crypto or Facebook.