Most of us here can really relate to what you're saying.
You can try to figure out the reasons but you probably already know. I'll bet you weren't a bad friend and that your friends aren't bad people. They are merely doing what they are being told is the right thing to do and don't yet have the ability to think for themselves about whether what they are doing is good or bad.
Regardless of why, it is what it is and you probably won't have a great deal of success in changing them. So move on and find ways of making new friends. Go to a night class or join some hobby group that interests you. Do you have kids? Or pets even? They can be a good way of meeting people and perhaps forging a friendship or two.
We've met up with and befriended a few people from this list and that was a big help during a period of time when it was easy to feel quite lonely.
Keep us posted!
Am