Spring Boot's popularity stems from its ease of creating standalone, production-ready applications and its support for container environments, featuring auto-configuration and embedded web servers. Moreover, a large developer community offers support. The post demonstrates containerizing a simple Spring Boot app using Docker in three steps: creating a Dockerfile, building a Docker image, and running a Docker container. The process includes setting up the Java environment, exposing ports, and specifying runtime commands. The successful deployment allows access to the application via port mapping between the host and the container.