VIEWS means CLICKED THROUGH. If someone SEES your meme IN THE STREAM and doesn't CLICK THROUGH, it doesn't count as a VIEW--even though they ACTUALLY saw it. I normally READ about 90% of the new memes in many of the streams I follow, but I only CLICK THROUGH on ones I UPVOTE.
SOMETIMES they get more views because they used a different image that actually made it a lot funnier.
But ASIDE from such cases, that's why MOST of the ALL-TIME LEADERS left about a YEAR ago--starting around then a lot of GARBAGE sits near the top for DAYS and GOOD stuff "falls off a cliff" almost immediately.
TO SOME EXTENT it can be affected by the TIME OF SUBMISSION and the TIME OF FEATURING. Obviously there are fewer viewers late at night, and NEW memes are CONSTANTLY being submitted. So if a newer meme hits when there are more viewers, it will get more views. And YOURS "falls off" before it has a chance to accumulate.