The Indian National Congress agreed in 1947 to the partition of the country mainly because

The principal reason the Congress agreed to partition in 1947 was the collapse of law, order and communal relations which left its leadership unable to prevent mass violence. Gandhi explicitly conceded the inevitability of partition, arguing that unabated communal violence and widespread participation in it across Punjab and Bengal had deprived Congress of the strength to resist division [1]. Contemporary records and party resolutions similarly state that Congress accepted grouping and partition largely because it could not stop the communal riots [2]. Senior Congress leaders also framed acceptance as a tragic necessity to avert far greater civil conflict, stressing that refusal risked prolonged communal bloodshed and possible civil war [3].

Sources

1. [1] History , class XII (Tamilnadu state board 2024 ed.) > Chapter 8: Reconstruction of Post-colonial India > Introduction > p. 101
2. [2] Rajiv Ahir. A Brief History of Modern India (2019 ed.). SPECTRUM. > Chapter 25: Independence with Partition > Why Congress Accepted Partition > p. 499
3. [3] https://ncert.nic.in/pdf/module/Partition_Horrors/Partition_Horrors-Secondary_Stage.pdf