Some of us, believe it or not, read the news and knew all of this already.
I think the point is more why plans didn't change once business took off in London after the reviews came in, given that several months have elapsed between the show closing in London and beginning previews in New York. Producers can and do sometimes change plans - take the first (pre-Broadway) North American tour of 'Mamma Mia', which opened in Toronto and did so well there that they built a second set for the road and established a sit-down company at the Royal Alex rather than close it at the end of the scheduled limited run. 'Groundhog Day' was always heading for Broadway - but the question isn't necessarily either/or. Andy Karl is the only performer from the London cast who is making the transfer, so it *might* have been possible for the production's creative team to quickly get a sit-down London production up and running off the back of the run at the Old Vic *and* arrive on Broadway on schedule this week - except, as I said, Matthew Warchus's (un)availability probably ruled it out.