Huang taiji married the Mongols only out of political needs, and married two widows to make the Mongols surrender quickly. Daikin was a dynasty without so many feudal constraints, and the people didn't demand so much from women, so there were many widows remarried at that time. As the king at that time, Huang Taiji had the right to marry any woman, but as the king of a country, he also needed to think about his own people. In order to win over various tribes in Mongolia, he adopted the method of marriage to stabilize the frontier.
Mongolian Horqin people surrendered to Daikin long ago, and Huang taiji married many women of this tribe to reassure them. The most famous concubines in Huang Taiji's harem who were married from Mongolia should be Da Yuer and Empress Zhe Zhe. The most important thing is that they are still relatives, because Zhe Zhe is Da Yuer's aunt, but they can marry a man together, which shows the efforts made by Horqin tribe to please Huang Taiji.
The two widows he married are very beautiful. Even if they can't bring him benefits, Huang Taiji should put them into the harem. Huang taiji found his concubine after defeating Chahar Ligdan Khan, and these two concubines were very beautiful. When Huang taiji saw them, he was a little tempted, but he couldn't explicitly bring them into the palace, and the ministers around him advised him to take these two women into the palace to handle the relationship with the Chahar tribe, and Huang taiji took them away with a logical conclusion.
Mongolian women are really beautiful. Now we can see that girls in Xinjiang and Mongolia think they are very beautiful, so Huang Taiji certainly likes such girls, so it is normal for him to marry so many Mongolian women.