Freedom is not a reason for this, certain things can effect the potential revenue you earn. For example the CPM can often change throughout the year, also in regards to the 4k views that you had, it could be that some were viewed by people using ad blockers so that wouldn't give you a monetised view on that video. I have included some information about CPM and monetised / non monetised views below :
CPM, or Cost Per Mille, is the price an advertiser is paying, per thousand monetizable views, on your videos. Each view is carefully reviewed and designated into either of the following categories.
Monetized Views
- YouTube defines a monetized view as: "a monetized playback is when a viewer views your video (i.e., a view) and is shown at least one ad impression or when the viewer quits watching during the pre-roll ad without ever reaching your video (i.e., an abandonment)." Basically, that means that the viewer must watch and/or click an advertisement on one of your videos to be a monetized view.
Non-monetized Views
- A non-monetized view, however, is when a viewer does not see an ad on your video, but it counts towards your view count. These are actually the most common view you will receive. This is how you can have 10k views one month, but only makes $3.00.
CPM brings a lot of factors into play like: the type of content you produce, audience demographics, audience residency (some countries don’t have a partnership program, so they may not be eligible for ads), tastes/interests, and many more. CPM also fluctuates a lot. During the Holiday season, when advertisers have their largest budget, your CPM will skyrocket and then drop during the Spring season when their budgets are at their lowest.