Google uses filters, which run in different intervals apart from the main algorithm and have different effects for a page or the whole website. This is why spammy SEO tactics often "work for a while" - until said computationally intensive filter catches them and often punishes the whole website. Prominent examples for these filters are Panda [0] and Penguin [1].

[0]: https://en.wikipedia.org/wiki/Google_Panda

[1]: https://en.wikipedia.org/wiki/Google_Penguin