Obito's mask hid him from TNJ and From people knowing who he was.
While being tobi, He was free from being obito, he was someone else and struck fear into people because they knew nothing about him.
Once he took off the mask, The people he used to know automatically recognized him and they knew him before he turned evil. In a way, Once the mask came off, He was under attack inside of himself and outside with kakashi constantly reminding him of the past and naruto being his exact opposite who is the better version of him.