Monero has a particularity : it is GPU mining and CPU mining copatible.
It's difficulty has ever been very high, probably because a lot of employees all around the world are mining it 24/7 with their office computer.
In the lasts days, Monero price has growing high and a lot of new miners are coming : normal.
Agreed ZenFr, I'm not saying it's not normal or expected this happened...what I am saying is: the
result of this happening has made Monero mining completely worthless...
as of ~ August 2017....MONERO MINING IS NOT WORTH IT AT ALL 