No content on Google is posted there by 3rd parties. Google does select what is displayed and, in the case of snippets, they go out of their traditional way to promote that content.
The use of the word "post" is my own colloquially imprecise language, the law actually states
> No provider or user of an interactive computer service shall be treated as the publisher or speaker of any information provided by another information content provider.
So content indexed by google absolutely falls under the definition of "provided by another information content provider"
Providing links is indeed within this definition. However, cards go beyond that: by selecting one out of the many results promoting it and possibly alterating its meaning by selecting which parts, and how it is displayed goes far beyond merely displaying content provided by others.
Of course, there is plenty of room for google attorneys to wiggle, but in the end the objective for them is to 1) give credibility to a source and 2) to get the benefits of being the providers of information.
> No provider or user of an interactive computer service shall be treated as the publisher or speaker of any information provided by another information content provider.
So content indexed by google absolutely falls under the definition of "provided by another information content provider"