There has been a lot of reasons to disable the Basic Authentication that I have explained in my previous Blog. And when we do disable Basic Authentication for the security, we need to keep mind with the management users. While Disabling Basic authentication for management users like Global Admins and others there might be problem
Basic authentication provides a well basic level of security for your client application. Although this is not recommended due to vulnerabilities and exploits that can simply expose the user password. Some exploits like Password spraying attacks and Brute Force attack. It was on the roadmap of office 365 for Disabling Basic Authentication on Exchange online.