Antonyms for the phrase "were a sign of" could include words such as insignificance, irrelevance, unimportance, and inconsequence. These words suggest that something does not hold any significance or value, and therefore cannot be considered as a sign of anything. Additionally, antonyms like coincidence, accident, and chance also convey the idea that there is no correlation or causal relationship between events. In contrast, synonyms for "were a sign of" include words like indicated, suggested, and implied, which all imply a clear cause-and-effect relationship between the sign and the event it represents.