HCU hit me hard and can't recover: what to do?

Last January, I decided to remove certain pages that targeted low-volume keywords and weren’t generating much traffic. Surprisingly, my traffic skyrocketed to 250 visits per day shortly after. However, not long after that, the HCU hit my website, and my traffic has since dropped to just 20 visits per day. I found it strange that removing certain pages initially led to such a significant increase in traffic. Is this a common occurrence? Would it make sense to try this strategy again now? I do have some thin content scattered across the site, and I’m actively working to improve it. On average, how long does it take to recover traffic after being affected by an update like this? And is full recovery even possible?