Where did I go wrong...?

My onions didn't become onions... I planted them when the seed packet said to and I left them in the ground way longer then it said I should leave them because the ones I pulled up didn't have an onion on the bottom.

So I've obviously messed up somehow - does anybody have an idea of where I may have gone wrong? I want to do better next year but I don't know what I have to differently.

Hopefully I can eat these like spring onions...