Why the Lakers do it? The Lakers get a couple of a reliable shooters in Fournier and Gordon, as well as a couple of creators in Schroder and Gordon again, while also getting themselves a defensive-minded center in Noel and saving themselves some money in the process. Paying the price of Horton-Tucker and a top-10 protected first-round pick is a reasonable price to pay for this type of haul.
Why the Rockets do it? They essentially exchange a few out-of-place veterans for a few more out-of-place veterans (who they can eventually buyout, waive, or keep around) and meet their asking price of a first-round pick for Gordon without much salary cap implications of them in this deal.
Why the Knicks do this? They rid themselves of some unwanted players in guys like Walker and Noel and shed themselves of a longer-term contract (albeit a very prolific shooter) in Fournier while bringing in what they hope to be a very solid playmaker in Wall and a young, athletic still-a-prospect in Horton Tucker, both of who can be off the team in a year if things don’t work out for them or the team. The main price they’d be paying in this deal would be the added salary, which is a small price to pay for what can be beneficial additions to the team.