I'm starting to blame myself
Why are you blaming yourself?
I have just learnt that I have become the main reason why my friends are not studying well.
You are very modest to take the blame for something even if it might not be your fault. Try to tutor your friends to make up for their bad grades and for your feelings. Nothing bad will come out of that.
But what if they start to hate me for intruding?
I'm sure your friends will recognize that you are trying to help, especially if you let them know that you feel bad for distracting them from studying.  However, if they really resist any efforts to tutor them, then you will know that they had no interest in studying, and that it wasn't your fault in the first place.