I've heard multiple origin stories -- one is the issue linked in the article. Another was that Dave Syer worked on a Rails project briefly and thought "oh, this isn't so bad".

Spring is a team of fairly smart individuals who tinker with experimental stuff all the time, so I would not at all be surprised if Dropwizard didn't figure amongst the inspirations. And they do keep up with what other folks are doing, so good ideas tend to be adopted into Spring pretty frequently.

Disclosure: I work for Pivotal, but not on Spring.