Looks like Nicaragua had no new cases for quite long time. If they have closed their borders and restricted all sorts of travelling (inbound and outbound), then I guess they are safe just like Nepal and other countries that had like 2/3 cases where the patients were dealt with. If they are doing proper and enough testing of their patients, and there are zero new cases, then I see nothing wrong with this. Though, yeah. You don't want to risk anything. A single infected person who hasn't been tested might infect the whole crowd making a huge mess!
Let me quote this article:
Experts in Nicaragua agree the government uses confusing arithmetic for propaganda purposes and to reinforce the idea that the health system has controlled the pandemic.
When he reappeared after a 34-day absence in the midst of the health emergency, President Daniel Ortega maintained the virus had been contained “with the limited resources” of Nicaragua and “with patience.”
The reduction of figures is not limited only to positive cases. Statistics are also applied to suspicious cases, so data is also always on the downside.
https://www.aa.com.tr/en/americas/nicaragua-has-unusually-low-number-of-covid-19-cases/1813537So maybe what we are getting from the government itself is not the true number of cases or death itself, so in a nutshell very questionable or maybe the government itself is hiding something. So people really think that their country is safe from this pandemic.
As @bisdak40 has said, this is gamble for the government to allow this kind of sporting events, really very scary.