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Wouldn't be possible to draw any kinds of conclusions with such top-line data. From this post, we don't know what the keywords are or which websites were involved in these movements. We'd want to be looking at actual keywords, looking in the WayBack machine to see how content on both sites changed, looking in Ahrefs to see if there are any matching link trends for either site Alexa score is ancient I wouldn't be looking at it any more to be honest. Regardless, it's not possible to check for black-hat attacks on "purple line" or "blue line", we need domains here! If you want a comprehensive audit of exactly what happened, no one can supply it for 'mystery' websites based on a couple of charts You're also looking at things in a very binary way. How do you know they didn't do something good **when **you screwed something up? Why does it have to be one or the other? In SEO usually there are a convergence of factors surrounding such large movements!

Thank you, that's kind of what I thought.