I'm sorry this happened to you, but I will simply answer your questions.

There are far too many reasons different people are either afraid of intimacy or unable to love others romantically to go into here. Instead of asking why, ask "where are the ones that are willing and capable?" and redirect your focus. Asking why so much will really be pointless.

You don't expect too much. Expecting to find someone that will reciprocate love and want a relationship is completely reasonable. But to expect it to easily happy happen and be easy to find is the part that is setting your expectations too high.

They are out there, but finding the right one will take time. More than likely it will happen when you're not looking too hard

Hang in there, my heart goes out to you, I'm sure it hurt to have this happen