I stumbled upon a MAL post. Which had a nice graph which displays that after a small peak in 2010, bleach had a significant drop in rank.
This same post also claims that this data was biased, as the ranking is determined per chapter. Aka, people didn't like the arc bleach was at.
This drop was also visible in the yearly sales
November 23, 2009 to November 21, 2010: 5th place by selling 5,204,193 copies.
Nov 22nd 2010 - Nov 20th 2011. 8th place by selling 4,187,258 copies.
November 21, 2011 to November 18, 2012. 12th place by selling 2,974,750 copies.
However, unlike in the below chart, the sales popularity seems to remain consistently above 2.5 Mil, until 2016, where it dropped to 2.2 Mil. Suggesting it's popularity just normalized, instead of really 'dropping'
So what really happened to Bleach? Did it really suffer from a significant drop in popularity as shown in the graph below? Or is this just misinterpreted data by a user?