What was the tipping point where spam won the SEO arms race? Feels like SEO has been a thing for decades, cat and mouse, back and forth and the outcome for the

What was the tipping point where spam won the SEO arms race? Feels like SEO has been a thing for decades, cat and mouse, back and forth and the outcome for the search user has been good/decent results for most of that time, there have been big corrections against spam like Panda but generally consistent good results.. then recently bam! huge downswing in quality, spam won the war? Or Google gave up? Seems kind of unbelievable that suddenly its all gone to shit, what changed?