The trade was made to boost the 2019 team. It did. The biggest mistake was over-rating our own pitchers and the older relievers who were signed as FA. Part of the off-season was aimed at ticket sales. Alfaro, Williams, Crawford weren't popular, either with the fans, or I suspect the manager. I thought at the time (still do) that the trades being successful depended on a few things:
1. Realmuto's prowess as a defensive catcher significantly boosting the pitching staff. I think this is one reason the team expected the pitchers to do better on the whole than they did in 2018. It seemed they were really down on Alfaro's defense and managing the pitchers. Realmuto's D has been as advertised, but he hasn't significantly boosted the pitching.
2. Adding a big FA bat. They added Harper, whose offense has been a little disappointing thus far.
3. Whether Sixto could get healthy again and stay healthy enough to be somewhere between a #1 and #3 MLB starter. He has returned to health. Still has to stay healthy for a while to reach MLB. If he becomes a #2 MLB starter, then we got creamed in tis trade. The Phillies were in a better position than anyone to assess Sixto's long-term health risk.
4. The Phillies saw a lot of starting pitching prospects to replace Sixto and felt they could afford to trade him. In addition to Sixto health, the success of those minor leaguers bears on the wisdom of this trade. Howard has been hurt and just about all the other prospects they counted on haven't fared well the first half of this season. If Howard were healthy and ready to join the Phillies and Medina, Irvin, De Los Santos, Gowdy, Morales and Garcia were doing better, the trade would look better.
Crawford is playing well, with almost an .800 OPS, although he started the year in the minors. His D is neutral. For some reason, the Phillies seemed very down on him. Playing him at 3B in 2018 did him no favors. He was hurt a lot and likely just wasn't ready for MLB (the same likely true of Kingery, despite a great ST, and he also likely wasn't helped by playing out of position last season). Despite starting the season in the minors, Crawford has 1.5 rWAR, so he is now racking up WAR at about the same rate as Segura. He likely is the better player going forward, but that may well not have happened in Philly.