Why did the emancipation proclamation score big in europe?

The European nations forbade slaver much earlier, so they were elated when they saw that America would stop the slave trade as well. They supported it widely.

The reason why emancipation proclamation score big in Europe its because people in Europe were a bit ahead of the curve in opposing slavery compared to Americans. They were still racist and imperialist, but at least they'd abolished slavery already in their countries, even in Russia. I hope this helps