I'm hearing Universal didn't surprise Disney at all with their June 5th reopening date. Both Disney and Universal were on the Governor's Reopening Committee, they both outlined their plans. Universal said June, Disney said end of August. Disney pushed really hard to have Universal blocked from opening in June, but the Governor and Orange Co. officials like the thought of that Summer tourist tax money, so Universal's plan got approved. Now Disney is back to the drawing board trying to figure out what they can can bring on line by mid-June with their now limited staffing resources.
This is not really a case of Disney being "caught flat-footed" as just the fact that the 2 resorts are in much different situations in regards to the ability to reopen.
Universal is still paying all of their full time employees. All they have to do is schedule them to work, train them on new policy procedures, and fling the doors open. It was in Universal's best interest to get the parks open ASAP and stop paying employees with no incoming revenue.
Disney, on the other hand, sent all their international and college program employees home and furloughed almost everyone else. Not to mention that they require 3 times the staff that Universal needs. It simply going to take longer to get the place ready for guests.