large spike
Glancing over your games. I do not think what you call large is actually large. You are in the hobby enthusiasts bracket, it seems. And not a professional struggling to sell games.
our marketing
Existing is not marketing. Marketing has a budget. If you did not spend that budget, you did not market your games. You might have tried to entice some people to play it. Nothing wrong here, as I believe you are a hobby game dev. Those do not usually have a budget above pocket money. And marketing on zero to no budget is hard. There are many topics about that question where people discuss it. I have yet to see a good answer to that problem. If it were easy, everybody would be doing it and everybody would be at square zero again.
how should we improve
Have a game that people want to play and be findable for those people.
Let's look at the tags for your quack game. You did not set a genre.
2D, Automation, Co-op, Crafting, Godot, Indie, Multiplayer, Pixel Art, Short, Singleplayer
Sooo. Is this a singleplayer game or a multiplayer game. You posted on Itch. All games here are indie. You have made-with-godot, you do not need tag-godot (that fuzzyness is on Itch. This could be better handled.)
You do not have https://itch.io/games/tag-factory , https://itch.io/games/tag-duck , nor other "interesting" tags. Glancing over the description, it might be intended as https://itch.io/games/tag-funny or https://itch.io/games/tag-silly . You are building a giant golden duck, come on.
Your screenshots are not really inviting. After taking the first hurdle of people clicking on your cover, what do they see? Some lame green grass and a guy with a shovel. Your cover image promised a lot more.
Maybe your analysis of your traffic can give you hints, how people found your game. If it was recent, read what no time wrote. If it was certain tags, maybe expand on that.
My guess is this for many popular games: they are good for streaming. Either funny or horror, or cool, mind boggling, or whatever is entertaining to show. And it was shown by a streamer or two. Then a cycle of unknown streamers latches on to such games to also show them and become more famous. That's why you will see a lot of comments with links to videos on popular games. But is has to start somehow. And it has to be able to sustain itself for a while. You need a good enough game for that, and lots of luck.
To gain a base fame and experience, you should consider joining some game jams.