Every audience has different pockets that the Facebook ad hits when it's running. These audience pockets is the reason why ad performance varies on a daily basis - some days have absolutely insane ROAS and on the others the ads just sort of die because they're not being shown to a very receptive audience. You can jump in anytime and make money too provided you have a little money to spend. $5 adsets won't do you much especially if it's a trending product.
That's also not how the pixel works. Ads optimize on an adset level which happens when money is spent (Facebook is learning on the go) and having a pixel with data in that niche definitely helps but a lot of factors go into your ad's delivery. Factors like bid, relevance, website speed(yeah,that's a thing) etc. Facebook assigns a value to your ad based on all those factors and if your score is better than the other guy, you're given a higher preference during delivery meaning your ads are shown first over the other guy..
