thats because people asked for brewmasters. brewmasters were a very popular class idea in vanilla and tbc and still got a good chunk of requests in wrath and cata.
blizzard just took the brewmasters and expanded it outwards instead of inwards. they may not have used the word monks but they were still asking for them.
i think if they gave them the mechs and some other cool cosmetic stuff they would do well but they would really have to push the pr. we live in an era where adventure time and steven universe are really popular, weird and goofy are in now more than ever they just have to market it right and show it off more