This is a business model question, right? Nothing prevents someone from making a great privacy focused browser and actually charging for it vs being directly (Brave?) or indirectly (Chrome, Firefox?) ad-monetized.

Also in this context, referring to "customers of privacy focus products" is technically incorrect, they are actually users. Definition of a customer is "someone who pays for goods or services" thus Mozilla's main customer is Google (accounting for close to 90% of its revenue). Maybe looking through this lens, relation of Firefox product direction and what its "customers" want becomes more clear.

edit: simplified for clarity