This article explains what the deal was and it's no big deal:
http://www.cnbc.com/2017/04/05/steve-bannon-reportedly-removed-from-national-security-council-in-reorganization.html
In late January, Bannon was given a full seat in a move that downgraded the roles of the chairman of the Joint Chiefs and the director of national intelligence. It is a highly unusual to give a political advisor a seat on the committee.
President Donald Trump sparked concerns with the move to make Bannon, the former Breitbart News chairman and driving force behind Trump's nationalism and populism, a permanent member.
Bannon originally served on the committee as a check against Michael Flynn before Flynn was ousted as National Security Advisor, a top White House official told NBC News. However, Bannon only attended one meeting and felt he was no longer needed in that role after the selection of H.R. McMaster as national security advisor.
McMaster, who Bannon wanted in the role, was given authority to reorganize the committee when he joined the White House, according to NBC.
The change also downgrades the role of Homeland Security advisor Thomas Bossert.
A senior White House official told NBC this was not a power struggle. The official said the White House was bringing back more of a George W. Bush-era-type NSC. The council will be more streamlined and the decision making more deliberative, the official said.