Because this mystery publisher Gazillion Entertainment is, according to the Venturebeat website, a highly ambitious company with over 300 people employed already across multiple studios (including the LEGO MMO developers Netdevil). So they’re deep in the MMO business, as you can see.
However, back to the deal with Marvel, there are not many details: apart from the fact that it’s a deal spanning a ten year period, we also know that all Marvel characters are covered and it’s not affecting other deals between Marvel and other publishers. So I guess that all we can do now is wait for the announcement of the first MMO from Gazillion and hope it’s going to be a quality product.