The Gajapati rulers were associated with the region of Orissa (now known as Odisha). Here's the reason for their rule in Orissa:

Historical Region: Orissa, located on the eastern coast of India, has a rich and ancient history. It was home to various dynasties and kingdoms throughout the centuries. The Gajapati dynasty, known for its rule in medieval Orissa, emerged as a significant ruling family in the region.

Gajapati Dynasty: The Gajapati dynasty was a prominent dynasty that ruled over parts of Orissa. The Gajapati rulers were known for their contributions to the culture, art, and history of the region.

Cultural and Historical Significance: Orissa is renowned for its culture, temples, and historical heritage. The Gajapati rulers played a crucial role in shaping and preserving this heritage.

Notable Temples: Orissa is famous for its temples, including the Jagannath Temple in Puri. The Gajapati rulers had a significant association with these temples and made important contributions to their maintenance and patronage.

Overall, the Gajapati rulers' rule in Orissa is historically and culturally significant, and their dynasty had a lasting impact on the region's history and heritage.

So, the correct option is [4].