Q: Why are light and other EM wavelengths drawn into a Black Hole?
A: Because all energy has the property of gravity, whether free to roam or trapped in a configuration we call "matter." We don't bother acknowledging the gravity of photons as we are unable to measure it. Of course, a source of massive gravity would draw in even photons of miniscule gravity.
Q: Could the fact that all energy has gravity explain 'Dark Matter'?
A: IMHO yes, depending upon how 'Dark Matter' is defined. It's an archaic default scientist behavior to consider anything with measurable gravity to be 'matter'. That is not accurate.