In my opinion, this is a realistic trade that is right in line with the way each of these franchises is going. Let's break it down by team.
Cavaliers: The rumors about the Cavs not wanting to pay Collin Sexton seem legit to me. I think they know that they are still years away from contending and getting some good return for him makes a ton of sense. Plus, the opportunity to get rid of Kevin Love's contract is too good to pass up. The idea behind giving up Jarrett Allen is that they are in a position to draft Evan Mobley, the long, rangy center out of USC. In terms of the return, Obi Toppin gives them another dimension of scoring ability that they have been missing from the forward spots ever since Love's myriad of injuries. Kevin Knox is still a project but could thrive next to the pieces the Cavs are putting together. Mitchell Robinson is a good asset to have as he would be a good backup option at the center or could be used in another trade as a sweetener. The first-round pick could and should be used on a shooter.
Projected lineup: Garland, Okoro, Osman, Toppin, Mobley
Knicks: The Knicks are in win-now mode. Julius Randle is a legit star and RJ Barrett is on his way to becoming one. They are not at all worried about giving up Toppin, Robinson, or Knox as they all are either replaced by better players in this trade or are not on the winning timeline. Adding Sexton gives the Cavs a dynamic scorer and a supreme competitor. He is a borderline star and the opportunity to be on a winning team and in a good culture can take him to the next level. Jarrett Allen fits the mold of what Coach Thibs wants at the center position. He is a long shot-blocker much like what he had with Nerlens Noel and Mitchell Robinson but is much more mobile and is a much better rebounder. If they and are able to work out a good contract with Allen, he could be a huge piece moving forward.
Projected lineup: Sexton, Quickley, Barrett, Randle, Allen
Thunder: The Thunder are taking the "Trust the Process" framework to the next level. They have been building a young core while rebranding some veteran players and using them as assets to build up picks and add young players. Kevin Love has the worst contract in the NBA and needs new scenery. Getting a first-round pick in this year's excellent draft is what is needed to get this done. I will also be going out on a limb to say that the Thunder will draft Scottie Barnes at #6.
Projected lineup: Walker, Gilgeous-Alexander, Dort, Barnes, Love