About two years ago I had so many friends that it was great. It was at my last job. But then, hundreds of us got laid off/fired. Only a handful of folks kept their jobs. It was a wonderful company and I miss seeing my friends each day.
Although I try to keep in touch, none of them seem to miss me (I miss them all terribly) or even want to get together. They've all moved on, got other jobs, got married, moved away. Also, two long time friends of mine got married and now are no longer interested in hanging out with me. This is embarrassing at my age (52) to be friendless, yikes!
When a business undergoes mass layoffs like yours, it can create a great deal of chaos for those who are laid off as well as for those who are left behind. Many people may have residual hard feelings for the company and may not want any associations with their former colleagues.
You say that many of your former friends have had significant changes in their lives since they left, including new jobs, new marriages and new homes. Changes like these can be disruptive to friendships although they aren't necessarily deal-killers. It sounds like you are used to making many of your social connections at your place of employment, which is understandable given the amount of time people you spent there.