There is no factual evidence that Social Media increases SEO rank, but it does matter. Take it this way, if your content is shared on a highly followed social media page. You will get massive organic traffic. When you receive more traffic and retain it that affects your SEO ranking. It may or may not affect your rankings directly, but it surely does it indirectly.
Off-site or off-page SEO is a process where you perform different off-site tasks to create your site awareness. Link building, guest posting, and Social media postings are all part of off-page SEO. Many other factors are included in off-site SEO work, but essentially it is all about creating your brand presence off-site to increase your website rankings.
Link building plays a very crucial role in SERP ranking factors. When Search Engines such as Google find your content through high authority websites. It affects your SERP ranking by a lot. It shows search engines, how credible and high-quality your content is.
It does not matter if your advertising on search engines or using SEO strategies to rank on top. Proper keyword research is necessary. Keywords are the queries that people type into search engines to find answers. When you optimize your content on the highest volume keyword, you will reach more people and generate more sales.