Congratulations on achieving the 1st position on Google for a keyword with a volume of 12,000! While ranking high is a significant achievement, it's possible that the lack of traffic might be due to several reasons:

Low CTR: Even though you're in the top position, if your title and meta description aren't enticing, users may not click on your link. Irrelevant Content: Your content may not be fulfilling users' search intent, causing them to bounce back quickly. Competitive Snippets: Featured snippets and answer boxes can decrease organic traffic, as users get their answers directly from Google. Seasonal or Trend-based: The keyword's search volume might fluctuate, leading to periods of lower traffic. To improve traffic, focus on optimizing your title/meta description, aligning content with search intent, and monitoring keyword trends.