We made the decision to move away from where we had spent most of our adut lives. We were actually moving back to the area we grew up in, back to family (and fairly central to our grown up kids).
We spoke to close friends about it, and they understood. There were 2 families I was sorry to leave, but now one has moved anyway, to provide childcare.
I am aware that in some areas that are becoming run-down (this has happened to a place I know well) that some 'left-behinds' feel rather abandoned to an area that doesn't provide the lively social contact it used to.
I wonder whether you / they had different expectations of friendship? This happened to one couple we were close to. Their neighbours were so angry that they were moving that they (the neighbours) have completely severed the friendship!
In the end, only you know who you have social obligations to. There are many posts here about the obligations we have to family - but mostly, in mainstream UK culture, we don't feel the same about friendship in normal circumstances.
So I think you just have to write it down to experience, and decide how much you want to be in contact with the friends. If you have a good time together and enjoy each other's company, then carry on, as and when you can. If they moan and make you feel bad, then they will lose you completely. Not your problem, really, even if you feel sad about it.