Whatever I speak or msg about within Signal App appears on my youtube Recommended - Lemmy.World

Using cheap basic android phone, ive noticed for the last few years and so have my friends, that whatever we discuss, appears very blatantly obvious on my youtube recommended feeds. I thought Signal was supposed to be private and sandboxed? If it is, then google clearly bend their own rules and peer into the app. Does this happen to you? what is the explanation? PS The Official Signal Reddit sub removed my post thread when I asked this question there.