what makes people abandon their friends suddenly?

it may be silly but it's what I feel. Feels like I lost some of my friends with no reason. suddenly we're not talking anymore. Some have new friends and you find them happy with their new circles.

During this pandemic, I always chatted first and check on them if they are ok, but that's it. no longer conversation happens. 

Thoughts that I maybe was a bad friend. Not worth of their time.

change is really the only constant thing in Earth.