Not direct malice, but naive over-optimism gone a little too far, perhaps. Krugman has written and spoken a lot about this in a way that's accessible to the interested layman. Search for "krugman optimal currency area", or see https://krugman.blogs.nytimes.com/2012/06/24/revenge-of-the-....

The point is that there are definitely economic benefits to the simplicity and low-overhead of currency union among equal and near-equal partners, but when economic conditions vary greatly between regions (or more correctly, when economic conditions change differently over time in various regions), there can be a greater benefit to having different currencies that can trade at different levels against each other to assist in the proper valuation of resources in either region.

There's no 100% right answer, and national boundaries are not necessarily the "optimal" borders for currency areas, but obviously there are practical issues to weigh as well.

So I think it's obviously wrong to say "the Euro is bad". It's a great thing for France and Germany and Belgium and the Netherlands and several other countries in the Eurozone. But expanding the Euro to Greece maybe was a bit too far.

That said, the EU could do a lot via policy to make up for the problems caused by the imbalance of economic conditions between Greece and Germany, but ... they aren't doing nearly enough.