This is just my speculation but I think the reason why NYK didn't push for Durant is that they aren't sure about KD's plan in the future. It might destroy their plan if KD suddenly changed his mind as signing him will cost them exchanging a possible future rising star in the draft pick.

If we look at KD's current contract in Brooklyn, the team made a gamble that on Durant's 3rd year, he has a player option, either he will stay or not in the team. In other words, the upcoming season is the only time wherein Brooklyn can take advantage of KD (because KD was being ruled out to play in 2019-2020 because of his injury.)

But whatever it is, I like Brooklyn Nets to be one of the contenders in the Eastern Conference next season. Their fans are waiting. I hope KD and Kyrie will be at their 100% healthy status. Like to see a much competitive Eastern Conference.