I doubt this has anything to do with "customers voting with their wallets".

I suspect it's due to investors realizing the fragility of Spotify's business model - thanks to some (high profile? ish?) artists abandoning them at the drop of the hat - and selling their stocks, resulting in a huge drop in market value. The company has already been steadily and significantly loosing value for the last year, so it probably didn't take much to convince a lot of investors to bail.