Google is sometimes vague about whether its rankings are influenced by social media. Nonetheless, put simply, the content in social media which has great engagement has much more SEO value than the content with low engagement.
If you stop and think about it, it’s logical. Given that Google’s algorithm is designed to find and rank high-quality, useful content for each search query, it obviously requires a way to measure the value of sites. Social media engagement provides Google with exactly what it needs: external validation of a page’s value. Because, like every other social media user, you’re not going to like a piece of content on Facebook, Instagram, Et al or share a link to any of them if you think it’s worthless. And you’re not going to spend your precious time watching videos that aren’t entertaining and/or informative. At least we hope so!