Earning in January 2020 is lower than the one in December 2019.
Simply it is just because companies don't spend money on advertisement.
広告費が高い月: 3月 6月 9月 12月
広告費が低い月: 1月 4月
Higher advertising expenses months: March June September December
Lower advertising expenses months: January April
I was surprised to see the earning was getting lower although the view numbers were increased but it seems that's how it is.