No, Capitalism was not a central tenant of, or unique to liberalism. This is widely cited by people on the Internet but it is simply wrong. Big-C Capitalism is something which has emerged independently in the post feudal world several different times, in several different forms. The central tenant of liberalism was, in fact, the notion that individual liberty is foundational to self determination and participatory government.

The people who push the "liberalism is capitalism" trope are poorly informed leftists who naively conflate all of the evils of modernity with the dominant political mode of the era. While there is definitely a link between two, this messaging is done in an intentionally misleading way.