Why would my website only show on page one for a few hours per day?

[SerpsGuy]

So I run a website that about a year ago was spammed to death by a competitor. My rankings slowly tanked, so I just left it and began a new website. Now, this old website is back on page one - BUT only for a couple hours per day. It gets 1500 visitors a day (between 1498 - 1510, specifically, like clockwork) for the last couple of months.

I thought maybe it was because google was shuffling, but it's been going on for awhile now. The website is not under construction, but a lot of my content was stolen and pasted to free blogs, and even on competitors websites. Infact page one has two other folks, one of which has my original content, and the other one has the same content I rewrote after the first guy stole it.

So maybe the site experienced duplicate content issues in the past from this, I dont know. Never received a warning in webmaster tools. No drastic changes to the site. Why would my rankings disappear and reappear so consistently that its as if google is throwing me a bone, giving me exactly 1500 visitors a month?

[Writerly]

Does it affect your new website? If yes, why don’t you save the content that you need for the new business and just delete old posts and pages? I think it's the best solution if you don't want to have the first website anymore. Has it ever shown the 404 error? It would be an indication that the page is “not found”, which means that the deleted content can stay indexed longer on Google and other SERPs. 410 errors, however, indicate that a blog post has been permanently deleted and informs Google that you have no intention of bringing it back. When deleting your old content, double-check if it’s being properly redirected to a freshly updated article. If you cannot redirect your old blog posts, simply delete them by using a “410 Gone” response code. This way you can bring the stealing of your content to an end.