I've never used webjars and don't really know much about it. Having said that, I did find a bug report on github that states that webjars doesn't work with JBoss due to the directory structure. (The report was filed against JBoss AS 7.1, but the architecture is still the same with wildfly.) The report is several years old, and I don't know whether there has been an update to resolve it. Somebody did publish a fix, but it's not official.
You may also need to put the webjars jar into your war's WEB-INF/lib rather than in your ear's lib.