https://blogs.fangraphs.com/lets-make-some-deadline-trades/Vientos doesn't seem like the type of trade player that the Cubs want. While the Mets certainly have a need for Contreras their minor leaguers make it difficult to see a trade work, so maybe Willson plus a reliever makes sense.
The Happ trade is light. Colas is interesting, but he's a soon to be 24 year old with 26 PA in AA. The Cubs are loaded at OF already too. Kelley was a big name out of the draft, but he has some serious control issues. Vera does too. I think that one is a bit forced.