I agree with this because over the time the Mongols were conquering, they killed millions. My person I had to research, Muhammad II, sultan of Khwarazm, one of his governors was killed by getting molten silver put into his eyes and mouth.

He killed Muhammad II's governor because Genghis Khan had sent expensive gifts in a caravan to Muhammad II, but the governor had them arrested, most likely out of fear, saying they were spies, and when Genghis Khan sent ambassadors to resolve the issue, Muhammad killed the merchants along with one ambassador.

Was there a reason the Mongols killed Qutuz's people? Did he do something to make the Mongols angry?

Muhammad II, sultan of Khwarazm:

I heard that Genghis Khan caught my Governor Inalchuq and killed him by putting molten silver into his eyes and mouth!

Muhammad II, sultan of Khwarazm:

Genghis Khan’s army defeated mine. He killed everyone, all 4 million of my subjects, and even killed the animals!

Muhammad II, sultan of Khwarazm:

Genghis Khan sent 200,000 of his best men and 3 of his best generals to fight my army!

The Mongols increased communication throughout Eurasia, this was a result of trade routes (like the Silk Roads) being used more because they were safer.

They also made trade routes (like the Silk Roads) safer for merchants/travelers, this promoted trade and brought the Silk Roads into its 3rd golden age.

They were tolerant of different religions, people who they conquered were allowed to keep their original religion.

They killed the people who refused to surrender, they killed millions and millions of people through their conquests.