Bulk API is a feature of Data Loader that allows loading large amounts of data into Salesforce faster and more efficiently. Bulk API uses asynchronous processing to handle data in batches, which reduces network overhead and improves performance. Bulk API is suitable for loading data files with more than 20,000 records or larger than 10 MB. The export file has more than 2 million records, so Bulk API should be used to load this data back into Salesforce faster. Reference:
https://help.salesforce.com/s/articleView?id=sf.data_loader_bulk.htm&type=5
https://developer.salesforce.com/docs/atlas.en-us.api_asynch.meta/api_asynch/asynch_api_intro.htm