You have the ability to manually specify the default visibility after a participant registers. This can be done in Configuration - Registration Settings - Participants Visibility.
This feature is used by organizers when they want to hide the participants list on the website until a certain number of participants are registered.
Participants are automatically visible
This is the default option for your events and it means that the participants will be visible to one another and, if the event is set to public, to the website visitors too, immediately after they register.
Please note that you can still change the visibility of individual participants on the participant list in the organizer's tool.
Manually turn participants visibility on
Participants will only be visible for other participants once their visibility has been manually turned on by the organizer and once they are activated.