Before we get into this trade, there have to be some assumptions for this to make sense.
Phoenix is underperforming. This team would be around .500 and no better than the 8 seed in the West. Maybe some injury issues as well, especially if a guy like Beal is out for the year.
Houston is slightly over performing. They are a top 10 team in the West and above .500 by at least 3-4 games. They are not title contenders but certainly a Kevin Durant away from being contenders.
The Knicks are having a great season, but they finally realize Randle plays best with spacing on the floor, so lineups with both Randle and Mitch are not as good as they could be. McBride is having a good season but not playing much due to the absurd guard depth the Knicks have with Brunson, Mikal, Donte, Hart, and at least one of Payne, Kolek, or Rokas able to give quality bench minutes.
With these assumptions out of the way, this trade solves problems for each team. Lets discuss why each team does it.
The suns realize, sooner than their owner wanted, that this big three cannot win it all, so aborts his 2 year plan to compete early. Trading KD for value now before he loses all value or enters free agency is key, and in return the Suns are able to get a collection of players and picks. To be clear, the package I sent is not necessarily what I think it will be. I will split the package into certainties and possiblities.
Defintely included: the 3 PHX picks from Houston, one first from the Knicks, McBride, and Precious from the Knicks, Brooks from Houston(for salary)
possibly included: another pick or some seconds from the Knicks, Tari Eason, Cam Whitmore, Jalen Green, Ja'sean Tate(not all of them a combination of 1-2 of them), maybe a couple seconds from Houston or another first. In return PHX is able to get 1-2 quality young players from Houston with potential in addition to their own picks back, as well as a 3 and d combo guard in McBride who will probably work better next to Booker than him running the point alone. This allows PHX to still consider competing with Booker down the line while giving up their chances for this and next year.
Houston gets KD. Pretty simple, a starting 5 of FVV, some combo of Jalen/Amen/Sheppard/Whitmore/Eason/Tate/Green/KD, and Sengun would be deadly especially with expected improvements from some of Sengun, Whitmore, Jalen, and Amen. They should be tier 2 or 3 contenders this year and one of the top teams in the league next year. They don't like losing Jabari, but its for KD so Jabari wouldn't even be playing much anyway.
The Knicks fix their front court depth. Resigining Precious solved issues for the time being, but over the season he proved to not be enough especially when Mitch went down to injuries. Instead, the Knicks trade for Jabari and unlock the full potential of the death lineup. Jabari fills in as their small ball 5, but at 6'11 he's not small at all and can guard centers, and the whole lineup is huge outside of Brunson(Mikal 6'6 7'1 wingspan, Og 6'7 7'2 wingspan, Julius 6'9 7'0 wingspan). Jabari outside of being a switchable defender onto the 3 through 5, was also a 38% catch and shoot 3 pt shooter last year(and clearly a very promising player overall). The Knicks now have a center in Mitch who can guard the best centers in the league well(watch the 6ers series before he got injured) and a guy in Jabari who can still offer good defense while turning the offensive unit into an absolute nightmare for opposing teams.
Starting 5: Brunson, Mikal, Og, Randle, Mitch
Bench: Payne/Kolek, Donte, Hart, Jabari, Sims/Hukporti(though Thibs runs a 9 man rotation usually)
Closing 5(dependent on game but most likely): Brunson, Mikal, Og, Randle, Jabari.
A little added benefit for the Knicks is Jabari and Randle are very much opposites at the PF position right now, with Jabari being a good shooter and switchable defender but lacking playmaking ability while Randle is a poor shooter and worse defender but has one of the best playmaking and post playing abilities in the NBA for a big so they can hopefully learn from each other in practice.