I have the same sentiment, Indeed does not seem to be a representative source for the tech jobs market. I have an impression that most postings there are for staffing firms and the number of their posts do not correspond to the actual vacancies (they might be all posting the same job or post fake jobs to collect resumes).

The drop could be just the result of some of those firms ceasing their activity as I definitely don't see as many CyberCoders and whatever was that bot, which automatically reposted vacancies on Linkedin (JobNetwork or something), in the recent months.