Cardinal fans who don't like the return don't realize how much money your free up by trading Arenado. You're not getting a huge haul for the contract he has remaining. Yes, he's a really good player, but there's a reason he's listed at a -16.6 value. For the Braves, this was a two-for trade. The Astros Trade got us a #2/#3 starter for the next 3 years, and three prospects who are huge upgrades in AAA. The Cardinals trade replaces the loss at third (from the trade with the Astros), gets us an amazing set-up man in Helsley, and Romero is a VERY solid left-handed reliever who immediately replaces Minter. That's 4 every day players, for Riley. Cam Smith "should be" the long-term replacement at 3rd, and the addition of Arenado allows him to complete his progression in the minors, until he's ready. Melton and Baez become legit possibilities to replace Kelenic, if he doesn't produce.

I don't think the first trade has to happen. Riley has played a passable LF before and could move there for this year then potentially move to DH when Ozuna is gone. The same scenario could happen if the Braves just signed Bregman.