You have to give credit to both MS's board and Steve Ballmer that they clearly held back on announcements until the new guy took over, so he could hit the ground running, but clearly a lot of the things he's been credited with were done under Ballmer (and I am not one to give credit to Ballmer lightly).
Still, he's clearly been a good pick (so far) simply based on perception.
Agreed. One doesn't simply wizard up Office for iPad in a couple of months (weeks?) or however long it was between SteveB's departure and the announcement. That said, almost all of them could have come out a year earlier or could have achieved a higher priority while under Ballmer's tenure. Perhaps Ballmer leaving gave a freer hand to those projects.
Either way, the people running Microsoft clearly want Nadella to succeed as an individual and they apparently want Microsoft to succeed as a company, given the business shift over the past few months.