Your article is from November, 2014. Had you done a little research you would have found that the bomb charges were not added until April, 2015. As far as why, goes? You'd have to ask the FBI and I doubt they'll tell you.
http://www.stltoday.com/news/local/crime...a044f.html
http://www.stltoday.com/news/local/crime...a044f.html
Quote: Bomb charges added against two men who allegedly wanted to blow up the Gateway Arch
- By Leah Thorsen St. Louis Post-Dispatch
- Apr 3, 2015