The primary advantage was time to market. When I started five years ago edX had a monolith that was deployed weekly...after a weekend of manual testing. The org

The primary advantage was time to market. When I started five years ago edX had a monolith that was deployed weekly...after a weekend of manual testing. The organization was not ready to improve that process, so we opted for SOA. By the time the monolith had an improved process—2 years later—we had built about three separate services, all of which could be deployed multiple times per day.