Hello,
Hive compaction runs first, then a cleaner thread waits for all readers to finish reading the old base/delta files. When it determines that nobody is reading the old files anymore, only then does the deletion of the old files occur. Please run SHOW COMPACTIONS and look at the state of the compaction in question.
Also would help to know which version are you on for CDH/HDP/CDP? If CDP, public or private cloud?
Hope this helps,
Alex