What was the most significant cause of the Ilkhanate’s collapse?

The Ilkhanate collapsed because it was devastated by the bubonic plague.
The Ilkhanate collapsed because of internal revolts by the Han Chinese.
The Ilkhanate collapsed because of the its support of Sufism. .
The Ilkhanate collapsed because the ruler did not have a male heir.

The most significant cause of the Ilkhanate's collapse was the ruler's lack of a male heir.

The most significant cause of the Ilkhanate's collapse was not having a male heir. To arrive at this conclusion, we can analyze the other options and eliminate them based on their historical significance.

1. The bubonic plague: While the bubonic plague did have devastating effects on the Ilkhanate's population, it was not the most significant cause of its collapse. Although the plague led to a decline in population and weakened the empire, it was not a direct factor in its downfall.

2. Internal revolts by the Han Chinese: The Ilkhanate was primarily composed of Mongol rulers and their subjects from various ethnic backgrounds, including Persians, Armenians, and others. The Han Chinese did not play a significant role in the Ilkhanate's collapse, so this option can be eliminated.

3. Support of Sufism: While it is true that some Ilkhanate rulers supported Sufism, a mystical form of Islam, it was not the main reason for their downfall. Sufism was practiced by a relatively small portion of the population, and its influence alone would not have caused the collapse of the empire.

4. No male heir: The Ilkhanate rulers faced significant challenges in maintaining stability due to succession issues. The absence of a male heir often led to power struggles among rival factions, thus weakening the empire and contributing to its collapse. This factor had a more direct and significant impact on the Ilkhanate's downfall compared to the other options.

Therefore, the most significant cause of the Ilkhanate's collapse was not having a male heir.