Q: What is the meaning of 'Reviewers Assigned' after a minor revision in Springer's Editorial Manager?

Typically, a reviewer’s decision falls in four categories: acceptance without revision, acceptance after minor revision, acceptance after major revision, and rejection. For papers accepted after minor revision, the revised papers are often published without another full process of peer review. The authors can still be asked for explanations for certain points raised by the referees if they had not been adequately addressed. Occasionally, the Editor-in-Chief may request additional review or comments on the revised paper (usually by members of editorial board) if it seems necessary. From your question, it appears that the Editor-in-Chief wants additional vetting of the revised paper and is following another round of peer review. Note that this might be the case for journals besides those published by Springer as well.

We have answered similar queries before; you might find the answers useful:

• What does "Editor assigned" mean after "Under review" for a revised manuscript?
• How long does it take for the status to change from "reviewers assigned" to "under review"?