Google updated its search quality evaluator guidelines back in August, placing a greater focus on the ‘E-A-T’ principles of expertise, authority and trust.
The first few weeks of the update was characterised by leading brands witnessing significant and sometimes erratic changes in their organic search visibility. Some brands saw their visibility almost wiped out entirely, only to return to normal shortly afterward. Weeks of volatility followed as Google appeared to tweak the dials on the updated algorithm.
https://www.affiliateinsider.com/2019/01/25/google-e-a-t/
Google has used links to determine the authority of websites since its early days: the idea of webpages casting “votes” for other pages by linking to them is at the core of the PageRank algorithm. This led to the rise of numerous manipulative link tactics. Google reacted with the Penguin update and manual penalties; link schemes evolved to outsmart the algorithm. New Penguin updates followed. The story went on for years, until it no longer made sense.
https://marketingland.com/use-brand-mentions-seo-linkless-future-link-building-232780/