The right question is why sovereigns wanted to wage war against France again and again ?
Because France completely unbalanced the military and economical balance of Europe.
And why could France do this ?
Because revolutionary, then imperial France turned the table on divine rights of sovereigns, uneven legal system, social segregations by aristocrats, state religion, corporatism.
As Thucydid already remarked, citizens outfight subjects. That is, when fighting one to one.