Knowing algorithm history prevents you from reinventing tactics that already got killed. The biggest updates of the last 15 years each killed a specific tactic and shaped what works today.
Targeted low-quality, thin content and content farms. Killed the "publish 10,000 auto-generated pages and rank for everything" strategy. Made content quality a ranking factor.
Targeted manipulative link-building, link farms, paid links, exact-match anchor text abuse. Wiped out sites whose authority was built on bad backlinks. Made backlink quality matter more than quantity.
Shift from keyword matching to entity and intent understanding. Foundation for everything that followed (RankBrain, BERT, MUM). Made search intent the primary target, not exact keyword.
Penalized non-mobile-friendly sites. The first algorithm where UX (mobile) was an explicit ranking signal.
Google's first major machine-learning ranking signal. Interprets ambiguous queries. Made it harder to game specific-keyword tactics.
Natural language understanding. Google could now understand prepositions and context ("can you get medicine for someone pharmacy"). Made hyper-targeted keyword matching less effective vs, natural writing.
Multiple broad "quality" updates per year. Each one adjusts the weights of hundreds of ranking signals. Drives the cyclical traffic fluctuations most SEOs deal with.
Sitewide signal that demotes sites with lots of content "written for search engines, not humans." Killed content-farm-style SEO that had persisted.
Added "Experience" to the existing Expertise, Authoritativeness, Trustworthiness framework. Strengthened reliance on first-hand-experience signals.
Google started showing AI-generated summaries above organic results. Shifted traffic patterns, informational queries lose clicks; transactional and specific queries largely preserved.
Every major update has rewarded the same thing: genuinely useful, well-produced content from credible sources. Every update has punished shortcuts. The future will rhyme.