How to view Docker image layers on Docker Hub?

This is now possible by clicking into the image tag on Docker Hub.

Docker Hub is quite limited at the moment and does not offer the feature you asked for.

When an image is configured to build from source at Docker Hub (an Automated Build) you can see what went into it, but when it is uploaded pre-built you have no information.

Use microbadger, which comes with a few badges as well, eg:

So your tomcat image on https://microbadger.com/images/tomcat would look like: