Yes its injuries, and its height and body type.....taller players are inherently heavier and experience more loading cumulatively and by later years more leg/knee problems. Suns are gambling on winning this and next 1 or 2 seasons with this trade banking on Durant's health. They will be somewhat deflated if injuries (think Kawhi Leonard and Clippers)
This is more like the LA Rams…throw all picks in for a chance at one ring then kinda be screwed for the next 5-6 years. Basically what the new Suns owner is doing, win at least one chip in the next 3 years and then be okay with being trash after and think of that as the cost of winning the chip. For a team that’s never a title , it’s worth it ofc if they do it.