Not really the race was cancelled so they are not racing. We don't know if they took a few days off when race was stopped as a mark of respect, or even stuck to the race route and rules when they started riding again.
The original race rules always offered the option of riders being able to complete the ride, even if they pulled out of the actual race. One rider Juliana got sick and was driven back to perth for medical treatment, then she restarted the ride as a non-competitor.
There are lots of reasons for riders to want to continue. Most of the riders aren't pro-racers, they are round-the-world and cross-continent riders. I think a lot of them want to complete the ride, so they can cross it off their list. Some riders were raising money for charities .. so they might have felt an obligation to complete the full ride. If a rider had come from OS, they might want to complete the ride across the continent this time, as they don't plan to come back.