Currently in order to see why the build failed, the first step is to go the status page for a build. If any projects have failed to build, there are shown here. But when the build has failed for coverage reduction, I can only see this in the console output.
It would be good if there were more details against the jacoco summary. These could include something like the warnings next generation plugin shown below where the quality gate is shown and the result. With this it would be good to see the same details as the console logs, e.g. which scope reduced and by how much.