I think it was not clear, for a long time, just how divergent Perl 6 would turn out to be. If you look back (way back) at the original RFC process, most people were proposing fairly minor changes to the language; and it was billed as an opportunity to clean up a lot of cruft at a one-time compatibility cost. Rather like Python 3, in fact. But then it bit off more than it could chew, and as you say it is now envisaged as a new language sharing some Perl heritage.