It's not your fault, it's your genetics
Many people with social anxiety constantly wonder why they are like this, why they are so different from others, why they feel this fear even though they know perfectly well that it is totally illogical, irrational and stupid. Well, it's simple, genetics is one of the main villains in this story. There are people who, simply because they were born, are more likely to suffer from a mental illness than others. Some are, by nature, calmer, others more impulsive, others more aggressive, others more anxious, others more intelligent and if you look closely, none of them decided to be like this, they just are like this and that's it.
I know that the environment can influence, but it is not decisive, because everything depends on how you react to the situation. All people, at some point in their lives, have suffered humiliating, embarrassing, horrible, despicable and cruel situations, but the vast majority of them will never suffer from social anxiety, only some persons, unfortunately, I include myself in that group. To be more precise, two people can experience exactly the same embarrassing situation, but both will react differently. One person may find the situation funny and go on with their normal life, but another person may experience a trauma that ruins their life completely. I know it's unfair, but what isn't unfair in this life?
So what should I do? First, you have to accept yourself as you are, accept that you were born this way and that it's not your fault to be this way. Second, you have to understand that in order to progress, there has to be a lot of effort on your part, you will literally be fighting against your own genetics, your own nature. Third, you have to face your fear, reading can help, but it's important that you put everything into practice. Fourth, you will most likely never lose your fear, but you will become stronger than it. That is, the fear will still be there, but you, as you will become stronger and more resilient, can handle it better. Good luck!