I want to break up with my boyfriend in the wake of his grandfather dying
Your boyfriend's grandfather dying caused you to break up with your boyfriend?
Yes, I couldn't understand why his grandfather is more important than me.
It's rude to creak up with your boyfriend when they are going through something difficult. It makes you look shallow and a bad girlfriend.
He should understand that I need him to pay attention to me.
Your boyfriend needs time to grieve and to spend time thinking about his grandfather. You dumping him in the midst of this process is inconsiderate. If you were in his shoes, you would want the same.