Timothy McVeigh, an agnostic, and Terry Nichols, an atheist, were totally incompetent. They'd tried to build bombs before and had failed. Nichols visited Manila the Philippines several times in 1994, supposedly to pick up a mail order bride, but she never went with him. These visits coincided with the time Ramzi Yousef, mastermind of the 1993 WTC bombing, was in Manila planning another attack. Nichols comes back to the US and he and McVeigh coincidentally create a very similar type of truck bomb that Yousef had used in 1993 and use it to murder 168 people and injure 680 others in Oklahoma City.
22 eye witnesses reported seeing a John Doe #2, a dark-skinned man who was later identified through photographs as Hussain Hashem Al-Hussaini, a former member of Iraq's Republican Guard who fled to America after the first Gulf War.
After McVeigh and Nichols were caught the FBI dropped all mention of John Doe #2 and said the case was closed. They were trying to avoid all mention of Islamic terror out of fear of having to go to war in the Middle East to counter it.
Jayna Davis was assigned the task of looking into the Oklahoma City bombing the day of the attack. Over the years she found connections to Al Qaeda and Iraqi sleeper agents in the US, along with a plot by elements within the US government to cover up the true nature of the attacks.
Here is part 1 of an interview with Jayna Davis about her book The Third Terrorist and the Oklahoma City conspiracy.