With careful crafting, by using different names; email addresses; phone numbers etc, you can craft different digital identities that are not connected in any way.
Algorithms being deployed by social media platforms are digging deep into our lives in ways that are not always clear. Your connections (what you like/dislike, who your friends are, what your political leanings are etc.) are powerful tools for advertisers and they are going to further and further lengths to make discoveries about you and connect you to their products. Often we do not understand how they obtain this information about us - they keep this secret as part of their business plans.
There are lots of examples where people try to keep some part of their life separate only to get suggestions of possible contacts or content to follow from their other parts of their lives that they thought were more private - here is one example