First a small correction: React has always been using that license (BSD + patent clause), it was only brought into attention again due to Apache foundation banning the license from its projects.
Regarding the question: the most critical difference is that Vue is not owned by a major corporation that has to defend itself or exert competitive leverage with patents. Facebook chose to enforce the patent clause to protect itself from patent litigations. In comparison, we do not own or leverage any known patents in Vue, nor are we a for-profit company that could become target of patent trolls, so we have no incentive to complicate our license with problematic clauses like Facebook's.
Even in the worst case scenario where a future version of Vue switches to a less-open license, all past versions of Vue are still under MIT, and can be forked if necessary. But as explained above, this is extremely unlikely to happen.