Link building is an essential component of the SEO. The more links you have on your site, the better it ranks.
Being placed within top positions in the SERP means that the websites would have extremely good quality and relevant content, that is capable of attracting genuine links from the other sites.
It’s quite daunting to maintain the top rank on a continuous basis and not all websites can cope up with that pressure. While some websites may find it easy and use simple and straightforward link building techniques; others can get deceptive and manipulative.
Thankfully it’s these unethical practices, that Google continuously strives to control. It supports the links that you have genuinely earned rather than ‘captured’ and ranks the websites accordingly.