How to better analyze and copy some website's success in 2023?

Hi

I know about 2 websites that achieved great success by same creator in same niche. How can I copy their strategy? What should I research and analyze?

More info.. Basically I've been in my niche for over 5 years. And I used to understand SEO and had good success in 2018-2020. But since late 2020 - I've been slowly losing traffic. Mainly thanks to all these new TLDs and the ability of anyone to copy the main player's website and go for it, right? I did too, with variable success. But I noticed this 1 person had really great success, even overshadowed and outpaced the main and way older players in the niche, on many keywords. Website main page is barely 300 words, so must be backlinks, right? But then I looked in the feature/change log and see that 1 website made it huuuuge like 30-40mil monthly visits according to similar web, and in just literally 5 months.. And then I found their other site, it's almost same niche, just different keyword, and again, they got to 3-4m monthly in just 4 months.. In both cases took traffic from the top player. And obviously shifted whole landscape, which negatively affected me even more.. They took our jobs.. How can we copy them?

is there any definitive guide on how to copy someone else's success? it's not like i want to take their bread, i want my bread back, that they took from me...

maybe a suggestion what are the best tools suited for this task? what to look into? am i asking something that's not OK to talk about on BHW? I understand this is someone's job, yet i'm just looking for a simple advice.. I would pay someone, but again, there's no recommendation.. anything?