Google will not necessarily show the rating stars, though, they check a few things first and may choose not to show, for instance, they check the overall quality of the site, and if the review content is representative of the main content of the page or not.
I have however noted that the rating stars are displayed when you search for the particular post as shown below:
Here is a quote from one of the Google’s help article:
We perform algorithmic and manual quality checks to ensure that structured data meets relevancy standards. In cases where we see structured data that does not comply with these standards, we reserve the right to disable rich snippets for a site in order to maintain a high-quality search experience for our users. Read our webmaster guidelines for more details.