Why is Import Management faster than REST API insert

Summary:

We would like to know the reasons why File Import via File Management is faster than via REST API insert. Can you please provide us comparison of each, in terms of Architecture, Structure, processes used? Great reference document is highly appreciated.

This would be used as a reference for the design of a project we are working on.

Content (please ensure you mask any confidential information):

Version (include the version you are using, if applicable):

25C

Code Snippet (add any code snippets that support your topic, if applicable):