Mike Waltz, who played a central role in the Signal-gate, is now out as Trump's National Security Advisor, but why did he decide to resign?

National security adviser Mike Waltz is leaving his White House post, although soon after reports about his departure were published, President Trump announced he plans to nominate him to be ambassador to the United Nations.

President Donald Trump has gone through his share of national security advisers. But he doesn't hold the record, yet.