Overshadowed
We can imagine auditioning for any talent show, American Idol included, has to be nerve-wracking. There are usually thousands of people that are all hoping for a chance to hit it big and become a star, and most of them are just as talented as you are. Often times, with huge audition crowds such as those that show up for American Idol, groups of 4 or 5 people audition together and get cut at this point. In that case, you better hope the people in your group aren’t as good as you are (or at least equally bad).
The last person you want on your group is someone as talented as Carrie Underwood. No one knew it at the time, but she would go on to blow away the judges and become a huge Country music star. Meanwhile, Robert very well could have been a good singer, but just not as good as Underwood. It’s hard to outshine Carrie Underwood, however, so he shouldn’t be too hard on himself.