Thanks for reaching out to us, if you want to get all user is through graph explorer you have to use pagination
https://graph.microsoft.com/v1.0/users?$top=999 , You need to follow the @odata.nextLink URI until you reach the final page (which is simply a page without an @odata.nextLink value).
ref doc - https://learn.microsoft.com/en-us/graph/paging
the other way to get all user at once, you have to try in PowerShell by using Get-MgUser
Hope this helps
Thanks