So most likely WhatsApp on your phone includes an engine that reads all your incoming messages and tells Meta that you are interested in some topic X based on y

So most likely WhatsApp on your phone includes an engine that reads all your incoming messages and tells Meta that you are interested in some topic X based on your recent messaging history. Meta is not per se breaking the E2E encryption, but their app contains a backdoor that reports some topic-level information back to Meta that could be used to deduce what you are talking about without totally breaking the confidentiality of your correspondence. (All this is just a guess based on OP's report and the above quote.)