Might have been wake turbulance from another F-18 that had just
departed.

Aircraft on the ground do not burst into flames due to wake turbulence.

George Patterson

Ain't speculation fun? I'm with you, George, wake turbulence, not.
Section (one plus playmate) and even flight (of four) takeoffs are done
without mishap. That aircraft is too heavy and the engines produce too much
thrust.
How come nobody has speculated on (1) blowing a tire, (2) collapsing a
gear, (3) combination of 1+2, (4) because of 1 or 2 or 3, rupturing a drop
tank or wing tank [nah, skip the wing tank -- bullet proof fuel cell there],
(5) rotor burst, (6) Al Queda attack.
Having some familiarity with military mishap investigation, unless some
kind soul in the CHINFO office wants to release the information or some good
journalist [been there, done that] can weasel it out, it will be months
before any kind of preliminary finding will come out of the Navy.
Meanwhile, y'all keep on spekleatin', y'hear.