Why do the Celtics do this?

They need to do something to fit this team. Outside of Brown and Tatum, this team is not a very good offensive team at all and they are very inefficient. Sure Vucevic isn't having his most efficient season ever, but if he looks anything like his Magic days then the Celtics will truly benefit, especially Brown and Tatum since they can take a load off of the offensive side of the ball.

Why does the Jazz do this?

They are a really good team, but they always fumble the bag in the playoffs, and the main reason nearly every year is because of the liability that is Gobert's perimeter defense. So, why not move off of him and his huge contract. Getting Horford wouldn't be that big of a drop-off since Horford is leading the league in blocks. Also, acquiring White and Williams will help the Jazz prepare for the future and end this era of Jazz basketball. Hopefully, a young core of Mitchell, White, Williams, and everyone else 25 and younger can be a scary team, 3-5 years from now

Why do the Bulls do this?

This is an insanely good offensive team, but there is one thing holding them back from being a true contender in the East, Interior Defense. So, why not get the best interior defender in the entire league. Adding Gobert will definitely raise the floor of this team and maybe even elevate the Bulls to the same tier as the Bucks, Nets, 76ers, and Heat. Also, getting Kleber to space the floor for Gobert and to an extent, DeRozan will be a great fit

Why do the Mavericks do this?

They get the most value out of a role player. Maxi would probably get you another role player and a couple of seconds at best, but they see that his value to a team that needs a stretch 4 is a lot higher than usual. So they capitalize on it.