As reasons why the port never happened? I don't really know, but the sense I get is that it just got too hard to find and sustain the kind of developer interest it needed. Again, though, I don't really know; my familiarity with coLinux tops out at having been an enthusiastic user, and even that was quite a long time ago now.

As reasons for WSL to happen anyway? It's hard to know, despite my earlier glib comment that it would. It's plausible that a 64-bit coLinux might have found enough adoption to provide the same support for Microsoft's Windows strategy that WSL does, although coLinux's FOSS licensing model would certainly complicate that a lot - but, on the third hand, how much does it cost to convince a dev team it's time for an acquihire and a community fork? And how much is WSL or something like it worth to Microsoft, anyway? I know a fair number of devs who are glad to have it, but the next I meet who actually switched (or switched back) to Windows for it will be the first.