France's fellow European countries viewed the French Revolution with a mixture of fear and revulsion. They issued warnings that France refused to heed, and eventually, large-scale war broke out.
All the monarchs of Europe were very disapproving of the French Revolution and terrified by it. They knew that what was happening in France could also happen in their own counties. Therefore, they decided to stay neutral (except Austria, which declared war on France, but didn't help the royal family).
They were afraid that if they openly opposed the revolution, their own people might revolt against them. They also couldn't support the French revolution, because the main purpose of the revolution was to get rid of the monarchial and aristocratic system in France. As hereditary rulers themselves, the other European monarchs of course couldn't support that.
