Google makes money by ‘personalising’ your experience. In practice, this means Google aggregates as much of your online and offline activity as it can in order to profile you as accurately as it can. The more accurate the profile, the better it can personalise your experience, and the more accurate the ads Google can target you with… and the more $£€ Google makes (off of you).
Go to https://myaccount.google.com/data-and-personalization, and scroll down to the activity section to see what personalisation settings are active.
You will want to go to each of the three sections and pause ‘personalisation’ – fortunately they’re all actually on the same page at https://myaccount.google.com/activitycontrols .