Hey there!
Your traffic data in your campaign is imported directly from your Google Analytics account. We don't change or alter it, so if you're seeing dropped traffic there can be a few different causes.
If your traffic in your Moz campaign is lower than what you're seeing in GA, this is likely due to a connectivity issue the prevented us from collecting your traffic data on a daily basis. Oftentimes this is caused by expired or invalid tokens. We recommend reconnecting that token to restore traffic data. You can double check this by heading into your Traffic from Search section and switching the timeframe to daily. You may see missing data points from the days it wasn't connected.
If your Moz traffic matches what you're seeing in GA (as it sounds like is the case for you), this might be an issue on GA's end. We would recommend troubleshooting with Google to find potential causes.
Traffic drops can also be due to SEO-related issues. Unfortunately, we can't diagnose SEO root causes for you, but you can definitely use Moz Pro to research why it might have happened. Did you have an increase in crawl errors that might be preventing people from reaching your site? Did a competitor make big strides recently? The Q&A forum is a great place to reach out to SEO experts who might be able to help. You might also consider reaching out to an SEO consultant to look into the issue!