Reposting this comment from Eric's blog for more context (PM on the Developer Relations team. We have been migrating blogs since 2017 and enabling employees to export / migrate their blog. To your specific issue, ex-employees that want their blog posts can email me dan(dot)fernandez(at)microsoft(dot)com and I’ll route to the support team. This does not include comments as the MSDN/TechNet blogs are not GDPR compliant (aka the right to be forgotten).

As for why, other community sites like TechCommunity are driving blogging at Microsoft for individuals, while product teams are looking to group official blogs (Windows, Office, and Visual Studio), and for blog posts that were really tutorials, moving them to open source documentation on https://docs.microsoft.com on GitHub. Customers ran into a number of issues where blogs provided out-of-date content/guidance that lead to support issues. For example, of the 16k+ blogs, 86% had not been used in 18 months and thousands were created with no posts or only a single blog post. Cheers,-Dan