FTFA: "We’d previously been using Chronos (with Mesos) as a cron job scheduling system, but it was no longer meeting our reliability requirements and it’s mostly unmaintained (1 commit in the last 9 months, and the last time a pull request was merged was March 2016) Because Chronos is unmaintained, we decided it wasn’t worth continuing to invest in improving our existing cluster."
Though Chronos has a release recently with a bunch of fixes, Mesos is inevitably fading as a legacy platform.