It's not that strange. Ask Madonna post "American Life". When your image is enough of a liability and couple it with a mediocre song, this is what happens.
"Gypsy" would have at least crossed some basic hurdles (ie. Top 20)
The difference here is, age(ism) plays against Madonna, Gaga doesn't share that obstacle and I'd also argue that post-AL Madonna released mediocre songs (sans MDNA, ofc). Not a good comparison with these two.
Turn Down for What is about 8 months old and nearing 1.5 - 2 million in sales, getting ready to enter the top 10 on radio. Crazy. Never would have expected this slayage.
Will be huge, year end for sales, radio, and Billboard as well. Wouldn't be surprised if it near the top 3 on year end. Top 5 is more likely