At that moment, with the crowd watching me, I was not afraid, or at least not afraid in the way you might have expected me to be and indeed as I would have been if I had been alone. I don't know if this makes it easier to understand or not but " in the ordinary sense" refers to a different type of experience of, in this case, fear so perhaps the writer is saying they would be physically fearful if they were alone but with the crowd in attendance thay were subject to metaphysical/emotional/psychological fear. It's difficult to be sure of the intention of the writer as this is just a fragment. As is a comparative here and you could substitute like in its place although like is more I formal

Hello! I am not sure if you are still looking for answers, but I will help. When the author says “I was not afraid in the ordinary sense, as I would have been if I had been alone”, they are basically saying that the character is NOT afraid. The author is using the word “as” to make a simile. They are comparing the (nonexistent) fear the character feels when they are alone to the (nonexistent) fear the character has when everyone is watching him. In the ordinary sense means something like… a basic understanding. Many humans are afraid of being watched by a lot of people, which makes it UNORDINARY for him to NOT be afraid. I will rewrite the text to make it simple. With the crowd watching me, I was not afraid, like you would expect. I was as unafraid as being alone. I hope this helps! I am sorry if this does not answer your question. 😅