Rav Yosef answered paskening that because when they were taken form home to the Coronotel they had to go quickly with little warning, and they got sick with no advance notice and some of them might have been weak and unable to exert much effort in preparing suitcases with enough clothes for the family for the entire holiday, and they cannot leave, they can do laundry.

Rav Yosef added that their situation is similar to that of someone who came from abroad or was released from jail on Chol Hamoed, and because there was no opportunity prior to the holiday to do the laundry (or get a haircut), for that person it is allowed on Chol Hamoed. The people in the Coronotel as well did not have the opportunity in advance to prepare (rather than just having left it to be done on Chol Hamoed), so they too are allowed to wash their clothes on Chol Hamoed. 

Combining that with those who are lenient regarding the use of washing machines on Chol Hamoed because it washes itself (and is not the tircha that is prohibited as it is by hand washing laundry), they are allowed to wash their laundry in the Coronotels on Chol Hamoed

source: kikar