Yeah, it helps it you think about this as a case.

Its Q3 2022. Spotify has spent $XM on loyalties, exclusive artists deals (e.g. Joe Rogan) etc. The overall user growth listening to this music and podcasts we paid for is decreasing. We forsee our users ignoring Spotify and prefering to spend time on TikTok, Insta etc for entertainment, curate music taste etc. We want to double down on user engagement and get users interested in Spotify. You are the PM in charge of the new Spotify. What do you do?

If your answer is "spend more money on music and stream that" - we already spent a lot, and not all artists are willing to sign Spotify deals.

Assuming they made a blind change. This design must have gone through a humongous validation phase to assess customer reactions

Nope, it's that they seek entertainment value elsewhere off-Spotify.

The answer is more nuanced than "some lazy leadership/siloed blah blah". Finding attention-holding UX patterns are HARD, especially on Mobile devices that compete with attention not just with other apps but also the user's external environment - you could look away from the screen due to any small reason. Hence, any pattern that is proven to work (e.g. TikTok's vertical content + scroll + personalized algorithms) tends to be copied. Its a paradigm that users already are familiar with, so the adoption+onboarding "cost" is lower.

Source - drove a redesign for an award winning Mobile app few years ago. Didnt work because it served retail which was hard hit by covid at the time.