For me the simplest way to understand it: Devaluing the currency is a good way to lower all wages in a country at the same time as well as taxing its wealthy without having revolution break out.
Really neat solution in a democracy: the uninformed don't realize what you are doing, the informed minority usually are wealthy with influence but: Since the really wealthy usually own assets internationally those don't get hit, an extra bonus.
Problem is it only works when you are the only one doing it, and evidently the Eurozone, Japan and the US are all democracies with a wage and tax problem.
And China really doesn't like getting more expensive too fast too.
In the end I think most will realize this economic war is a little bit futile, and hopefully we all get back to the real issue: creating meaningful work and distributing the wealth in a reasonable way.