Why didn't he order Hillary to stop? For that matter, why did Obama then create an anonymous, private email for himself to communicate with Hillary through her server regarding state business? And why did Obama lie when he told reporters that he didn't know that Hillary had a private server?
Everyone working in the West Wing knew that there problems with government servers which were woefully inadequate to the needs of Cabinet Members and senior staffers. That's why Colin Powell and Condi Rice both used private email. It's why the Bush Administration kept a private server in the White House, and why the Trump Administration is doing the same.
Furthermore, right wingers keep going on about the Clinton server as if it was like my internet access. This server was set up with security protocols designed for a former President of the United States, a man who still has Top Secret security clearance, and has proven itself to be far better protected from hacking than any US government computers.