When you see a stray dog and they are aggressive you need to ask yourself about the reason behind this. It is never because they are mean, or evil or because they hate people, it is because they are scared, simple as that. Life hasn’t treated them well in the past and they are usually traumatized so they try to defend themselves preventively, even when they are not attacked.
This man knew this and that’s why he tried so hard to reach Lena and to try to help her in spite of her defensive attitude. He was persistent and it paid off. Just look at how she transformed!