This is how sales are controlled by Amazon and distributed among sellers. Amazon boots you to the second or third page of the results so competitors spend some time in the spotlight, and during this time you get no or few sales. Amazon has the conversion (sales) data, and they can rotate to another seller once you have reached a pre-determined number of sales or total order value. Google does the same thing with Adwords, though Google does not have as precise data as Amazon has. It’s all highly manipulated and designed to keep sellers engaged, particularly those spending money on advertising.
If you sell consumables, such as items that must be regularly re-ordered, the impact of the rotation as noted above is felt less.