What causes a massive star to explode?
So a star can't shine by itself, so it fuses elements to shine and technically keep it's mass from collapsing.
A star fuses hydrogen, then helium, and etc, but when it gets to Iron, there is no product coming out of it, so that means no production, which also means that a star cannot hold itself up anymore, so it collapses.
In massive stars, this collapsion is HUGE, and since it is so huge, it explodes, sending out it's star guts everywhere as a supernova, and the remainder of the massive star is a black hole or a neutron star.
If the star was less massive, there wouldn't be a supernova, or in this case, an explosion.