Hello dear @culgin.

It would be a high risk to the security and privacy that WhatsApp offers to its users until now, if the "end-to-end encryption" was eliminated. It is precisely this encryption that offers a sense of security to users and is perhaps the main factor that motivates the adoption of this means of instant messaging.
Facebook has the domain of the information of those billions of users who innocently place private data on that platform. When merging with WhatsApp and eliminating the encryption, the recipe would be completed.

As for monetizing. To send ads more effectively it is necessary to know the inclinations and tastes of the potential client. Then without encryption this will be possible.

All best, Piotr.