None of these examples fits your argument, and almost all of them are entirely incorrect in how you've characterized them. And you've chosen to ignore both what I've noted about the second apron and my ask for examples of teams and players in the upcoming offseason that might fit your description, responding instead with an irrelevant and largely incorrect list of cap dumps instead. Why?
Minny giving up the superior talent in KAT for Randle?
That was done out of a desire to save dollars, particularly with the impending need to pay Reid. Minnesota remained far over the second apron after the trade, and looks poised to be there next season as well should they retain him.
Dallas giving up Hardaway Jr?
THJ was a negative-value player and no longer a viable member of the postseason rotation (he went on, not unexpectedly, to be a negative-value on-court player and a bad postseason performer with the Pistons as well). Dallas was not above the 2nd apron. They paid to dump him toward the end of being able to use the full NTP-MLE to retain DJJ (or so they planned; he signed with the Clippers).
Heat giving up on Butler to the Warriors?
The Heat were not above the 2nd apron either. They dealt Butler because he demanded a trade, and he demanded a trade because Riley was unwilling to extend him at Butler's asking price, and Riley was unwilling to extend him because of Butler's propensity for injury. Dumping cap had nothing to do with it, and trading Butler definitively ended this iteration of the Heat's ability to contend in the postseason.
Pelicans trading away Ingram to Toronto?
The Pelicans were not above the 2nd apron either. The iteration of the Pelicans that began this season is dead, the team is facing a rebuild, and its front office intended to have Murray replace Ingram anyway. They had no intention of extending him, so they traded him. Dumping cap had nothing to do with it.
Memphis trading away Smart to Washington?
The Grizzlies were not above the 2nd apron either. They traded Smart in order to open up cap space for a potential renegotiate-and-extend of JJJ's contract. Smart has missed the vast majority of these past two seasons and has negative trade value, and the Grizzlies paid a first-round pick to dump his salary.
Hawks trading Hunter to Cleveland?
Atlanta was not above the 2nd apron either. Hunter is on an affordable contract. He was traded because his health is eternally unreliable, the return was good, and Atlanta is facing a rebuild.
All of these trades involve dumping players for cap reasons.
Only two of them involved dumping players for cap reasons, neither of the players involved in those trades was a positive-value contributor, and, more pertinently, not a single item on that list fits your scenario of teams trading useful rotation players to get or stay below the 2nd apron.
I haven't asked you for such examples, because -- as I've mentioned -- there aren't any. Now, will you answer my question and list any examples of teams or players who might fit that scenario in the upcoming offseason?