While the WWE draft was slated for June, Vince McMahon has been toying with the idea of having two drafts every year instead of one, with one taking place after WrestleMania and the other taking place after Summerslam.
So the decision was made to experiment with a "Superstar Shake Up" as it wouldn't make any sense to hold a draft twice a year when every other sport has one. So the thought process was that if they didn't call it a draft now, they could still do a draft later in the year if they wanted to. Although it hasn't been decided yet if either roster retooling will end up being called a draft at all.
The shake up was announced on short notice and it's been debated through the weekend whether it should simply consist of a small handful of trades or if it should be a major change to the rosters like the draft usually is.
But regardless, with all of the injuries and the depleted star power, Vince has decided the company needs more flexibility and only having one opportunity a year to switch top talent to the other brand was too restrictive.