User blog comment:Zaarqawi/Why players from YGGDRASIL have been transported to the New World at various periods of time./@comment-27131588-20151108142213/@comment-27131588-20151108172728

And yet, this explanation has the most sense

Why the players were transported in different timelines? Because they were in different places, or even worlds. Why they were transported in groups? Because they were in same zones/guild houses/etc.