They own a big chunk (possibly a majority) of Spotify and extract hefty licensing fees from it. (Spotify moving into podcasting was apparently intended to find a market in which they could keep the profits.) The majors get far better licensing terms than indie labels or small artists would get, because they have the whip hand: Spotify has no choice but to pay up as not to become a platform without Taylor Swift/Ed Sheeran/Baby Shark/etc., which would effectively wipe them out.

Make no mistake, the three major labels (Warner, Sony and Universal) are reaping the vast majority of profits from Spotify.