I believe the issue was that Perl 6 had too many changes that made it hard to convert apps from earlier version.
That created some kind of limbo where people weren't sure if they should use perl 5 or perl 6 (”why develop in perl 5, when it is probably a dead end and perl 6 is the future” and at the same time "why should I convert to perl 6, what if it will be a failure and I wasted my time?")
By renaming it, it revives Perl 5 so developent can continue, and at the same time Perl 6 is presented as a new language, now whichever wins will be based on its merit.
That created some kind of limbo where people weren't sure if they should use perl 5 or perl 6 (”why develop in perl 5, when it is probably a dead end and perl 6 is the future” and at the same time "why should I convert to perl 6, what if it will be a failure and I wasted my time?")
By renaming it, it revives Perl 5 so developent can continue, and at the same time Perl 6 is presented as a new language, now whichever wins will be based on its merit.