Sometimes the President initiates them and explains to some aide what he wants and the aide in association with
other aides drafts it, and sometimes an agency that needs an executive order initiates the drafting of it it and then presents it to the President for approval with an explanation.
If it wasn't Bannon, it was presumably
drafted by some
other non-lawyer
aide of President Trump in the White House Office, and probably not by someone affiliated with the Department of Homeland Security, or with the Secretary of State's office, either of which probably would have
drafted the Executive Order differently.