Having previously worked at a place where it took minimum 3 months to hire someone (but often 6-12), I'd be amazed if Canonical actually ever gets to hire their first choices. What happened was this: By the time the first pick hires had been cleared, they had gotten another job. Same with second pick. Maybe even third, too. Most people don't have the luxury or will to just sit and twiddle their thumbs for months and…
In addition, Canonical is HQ'd in the UK, so it's not quite as easy to let someone go if red flags come up.