When people let you down

 I wracked my brain about why a person once close to me let me down. This was out of character for this individual and I have no idea why they are simply not available anymore. They've essentially ghosted me and the responsibilities we shared related to a common denominator in our lives. Why?

I've read a several articles and discussed this predicament with a number of people without using a specific name or identifying information. I've learned that this is not uncommon. Sometimes when situations get tough, people simply bow out, leave, or ghost. 

Some have pointed to the fact that we simply don't know what's going on with others--we don't know the factors that are pulling or pushing them away. We don't walk in their shoes, and we have to respect that. Yet, it doesn't make sense to me because the individual's choices seem so out of character for him. Why?

I could ask, but I've done that before and have not been met with a positive response or open attitude. In fact, it's been quite the opposite and I don't want to set myself up again for such a hurtful backlash. So I simply have to accept this fact of life. We don't see things the same way. What's important to me is not important to him. We're making different choices which is greatly compromising the once positive work we did together. 

I'll give it time and space. That's the only peaceful solution I can see. It's not easy, but I guess it's the way it has to be. Do you have another solution?