[link to rt.com]

according to this article

the plane landed nose first
then the wing exploded into a fireball

so the explosion didn't happen til
after touchdown

it also made 3 attempts at landing,
by-passed the first 2 times, waved off
and went around for another pass

so there were malfunctions somewhere

probably hydraulics related if the
nose gear didn't come down

I would say mechanical or maintenance related
at this point

go-arounds are usually common when landing gear
are not properly extended and locked

or could be sabotage on the plane