I will preface this by saying I have been close to the event in the past (not anymore) and am sharing my personal feelings only.
1) It is devastating news that the event is called off for this year, but it is the right call if you truly put the safety of athletes ahead of everything else (which as an event organizer, you absolutely must do)
2) This has nothing to do with $. People think Nike makes money on these events. I promise you that is not the case. It is a massive operating cost to put on 8 Regional Events and then Nationals. Flying 400 kids + staff from all over the country, booking the week before in many cases alone would wipe out most of the money made from Regionals alone.
3) People will complain that the decision was made "too early" - the reality is that planning for these events takes a long time. Would have already been in progress for many months. There are state/local regulations to work through, staffing, permits, vendor contracts, etc. You end up too far down a path and then cancel, the ramifications go beyond just the athletes.
4) Many teams plan their training based on running regionals and nationals. This can impact their summer training plan, race schedule, etc. It FEELS early, but the reality is that you'd have many teams scrambling if this decision was made in 1-2 months.
Just my opinion on this one. It sucks. No way around it, but i don't think the team could have made any other call or waited much longer.