Actually, this is a historical issue, but as I witness what is going on with the Hazara people right now, in the 21st century, it's because of the after-effect or the consequence of the fatwa or the jihad given by King Abdur Rahman in 1891-93 that they consider the Hazara people as infidels, and they also enslaved the Hazara people and forced them to be displaced. Their lands were given to non-Hazara people. Some of the witnesses also mentioned what happened in Uruzgan province, and the same in Kandahar, which originally was the land of the Hazara people. They were forced to flee the country. Most of them went to Pakistan, but some were not able to cross the border towards the northern parts, which were Russian countries at that time.
Unfortunately, those who were inside the country were all subject to the fatwa or jihad that was decreed by King Abdur Rahman. Mainly, that happened because of the Hazara people belonging to a minority sect of Muslims, which is Shia. That was a very easy tool for King Abdur Rahman to consider the Hazara people as infidels and subject them to genocide as infidels.
Unfortunately, that has given the mentality among the Afghan society that, as secondary citizens, they don't have the rights to live in the country. They are always targeted, even psychologically, which, as some other witnesses also mentioned, made it easier for society to have a recruitment pathway in the south of Asia for the extremists to go and to kill the Hazara people as infidels. That's what made the Hazara people a soft target during the current situation. It's based on the fatwa and the jihad that was given by King Abdur Rahman.