While I understand why a large discrepancy between the two is concerning, it is very difficult for us at Marketo Support to speak specifically to how Google Analytics pulls its metrics as compared with Marketo's Analytics.
I can only speak to what I know about our Analytics reporting, and it is based on how many times a lead performs the activity of visiting a web page, which must each have Munchkin on that for reporting. It is based on the number of times the web page visit happened regardless of whether it was the same lead viewing it multiple times or unique leads each time. I am not sure of the algorithms that is used to calculate the results for GA.
In a landing page performance report, Conversions and Conversions %reflect the number of times someone filled out a form and the Total Views are based on web visits. For Marketo, if one lead visits a web page 5 times, and this shows on the Activity Log, this will count toward the count for Total Views 5 times. Based on the document from GA, the pre-calculated data "relies only on the the number of sessions n the given date range and the time of each session".
As stated above GA has its own way of reporting, and we can only tell you how Marketo reports. If someone is cookied already and clicks a Marketo email, and they land on a Munchkin tracked page, you will see the web page visits corresponding to the clicked links. There are exceptions as the article explains that security software often gives a conflacted reporting on clicked links and sometimes web page visits as it scans the email to confirm they are legitimate links with no malicious code.
These clicks and visits are sometimes mistaken as people. Marketo does not distinguish the different but instead reports on clicks regardless. You may also refer to the below blog from one of our community champions on the same: https://nation.marketo.com/community/champion/blog/2015/08/25/integrating-google-analytics-with-marketo Marketo does not have a native feature to control bots or crawlers, however you can go ahead and set up: ReCAPTCHA Validation https://nation.marketo.com/community/champion/blog/2017/10/30/common-form-faqs https://nation.marketo.com/docs/DOC-3101 https://nation.marketo.com/docs/DOC-5601-preventing-search-crawlers-on-a-page-level-basis