Lively and Gafford are redundant, but Jalen's an outside shooting big and can be a double double threat off the bench, so there's more versatility. And Lonzo is the perfect combo guard next to Kyrie - two way, pass-first playmaker (they lost that with Luka obviously), big (6'6) can catch and shoot when Kyrie drives and kicks, can lead the offense and take the defensive perimeter assignments. Mavs top 8 rotation for the playoffs looks like they can beat anyone after this trade.
Knicks desperately need a center, so chicago reroutes Gafford. They also get off Robinson who never plays (halfway through the season, still hasn't played - which is normal for him).
Chicago takes all the bad contracts and old/injured guys, but they're compensated fairly for both what they're giving up, as well as what they're taking back. Wins all around.