Could you elaborate on that?
Many many years ago I had the displeasure of being in charge of an AD to OpenLDAP+NFS migration for a mid-sized company. I was put in charge after an intern had spent months trying but failing to come up with a migration plan. I can tell you it wasn't fun. Especially the weird configuration files and stupid Perl scripts I had to use to communicate with OpenLDAP. I don't remember the details, but there was a lot of character encoding problems (åäö) and places where whitespace was significant in command line arguments.
It made me appreciate AD because in comparison configuring that is a breeze. I'm not much a MS fan but AD is imho a solid product.
LDAP and Kerberos were in use before Active Directory, of course, but they weren’t ubiquitous the way HTML, HTTP, or IP had become by 1999, so I’m not sure the “embrace” stage of the strategy fits. Certainly, there were marketing advantages for Microsoft from using well-regarded open standards with at least nominal cross-platform compatibility, and some customers who would have expected any serious directory server to work with LDAP clients.