The answer is in this Google+ post:

https://web.archive.org/web/20140928104327/https://plus.goog...

   Scott James Remnant
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   +Michael Hasselmann at the point that Kay, Lennart and
   I sat down and discussed all this stuff, I don't think
   Upstart was perceived as "shitty" at all. We'd had
   on/off discussions for ages, but the big one I remember
   was the LF Collab Summit in SF in April 2010.

   Hindsight certainly lends a different perspective, and
   I'd be the first person to say that Upstart doesn't
   work as intended. +Lennart Poettering makes a great
   point about mountall in a recent post, it was written
   because Upstart couldn't do the complex filesystem
   cases it was designed to be able to do; and I was very
   aware even at the time that was a failure that would
   need to be addressed.

   Had the CLA not been in place, the result of the LF
   Collab discussions would have almost certainly been
   contributions of patches from +Kay Sievers  and Lennart
   (after all, we'd all worked together on things like
   udev, and got along) that would have fixed all those
   design issues, etc.

   But the CLA prevented them from doing that (I won't
   sign the CLA myself, which is one reason I don't
   contribute since leaving Canonical - so I hold no
   grudges here), so history happened differently. After
   our April 2010 meeting, Lennart went away and wrote
   systemd, which was released in July 2010 if memory
   serves.

   So I don't think I can claim that the perceived
   shittiness of Upstart spawned systemd, because at the
   time it wasn't seen that way. I don't think I can even
   claim that it provoked Lennart in any way, init was an
   area all distributions were fiddling with, so it was
   inevitable anyway.

   I entirely agree with Kay and +Greg Kroah-Hartman  that
   it was the CLA that caused systemd to be written
   instead of Upstart.

   But I don't need that self-affirmation anyway :) I
   wrote Upstart, I got paid for it, I moved on to do
   other things, something else came along and replaced
   it. If Upstart hadn't been under the CLA, and systemd
   hadn't've happened, all my code would have long since
   been rewritten by now anyway.

   That's the nature of the software world, there's no
   point getting precious over things. Do your bit, have
   fun doing it, move on and let others do their bit,
   etc.