i don't know when and where they contracted it and from whom and in what setting but it would suggest they all infected each other but who the host transmitter was we will never know.I dont know what they were there for, so not going to presume it was poor judgement or not.
they should have been tested prior to the flight and if any of them or all were positive they should have stayed under quarantine in Dubai until they tested negative.
if they did test negative then they could have contracted it on the flight which is always a risk when people are boarding having come from far and wide in many cases.