For people saying Pinterest has mastered SEO and that's why they're at the top, what exactly are they doing that is so effective? I'm not understanding how ind

For people saying Pinterest has mastered SEO and that's why they're at the top, what exactly are they doing that is so effective? I'm not understanding how individual Pinterest pages or users would gather that many quality backlinks for example. Do they have quality backlinks? If not, why is lack of backlinks not hurting their rankings?