A lot of times after leadership changes or acquisitions, executives have a foot out the door on the day of the announcement. But after Reid Hoffman stepped down from LinkedIn seven years ago as chief executive, he kept showing up, four days a week, and has continued to do that ever since. Now that LinkedIn is no longer a public company, but owned by Microsoft, he said he continues to plan to play a major role — and is very interested in helping Microsoft tackle challenges like artificial intelligence and quantum computing.