Of course people have bechirah. If the person who went OTD did so as an adult, it might be a different story. However, a lot of times with people who go OTD, the process starts when they are very young -early to mid teenage years. There’s a reason why they are called teenagers and not adults. There’s a reason we don’t marry off our kids when they are 13 and 14 years old. People are usually not mature enough at that age! For the same reason, kids sometimes cannot handle what is put in front of them at that stage in life. They don’t have years of life and decision making to look back on and take them through their troubles.
I can’t answer WHY Hshm gave them those challenges if ultimately they did not pass them. Maybe they weren’t meant to pass them. I don’t know. The whole concept of bechirah is so complicated and there’s much I don’t understand about it. I can only look at the parts of life that I (think I) understand and go from there.