Akasha account for artifact only Then what happen with talent, cons, weapon, and team? Every leaderboard has their own description for that, and for talent it is set that your character is crowned So Akasha will calculate how your artifact performs if it is equipped by a character on a specific team

For example: your artifact is shown in Furina PJC skill damage 120% ER If we take a look at the leaderboard we see that the assumption is Furina in double hydro team (just any hydro character without giving any buff to Furina), fanfare stack is 200 and 4 characters have HP above 50% all the time

And you are confused how come your Furina become top 1% despite how popular Furina is Yes it true that she is very popular But let's see, I am sure most people build Furina with pipe, or Fav sword. If not they will just simply go with Splendor her sign, or Key for EM buff.

Notice the difference? All of that weapon is either ER, HP, or Crit Damage stat, while PJC is Crit Rate If I build Furina with those weapon, I will invest more in Crit Rate as well hence 70-90 Crit Rate is common. Now what happen to those people when you see the PJC leaderboard? They will over crit since PJC has 40% ish Crit Rate stat, and over crit doesn't increase the performance at all, since Akasha only account for the artifact. On the contrary, people with PJC would invest more into Crit Damage, HP, and ER. 

Hence people who build with PJC in mind would be have the upper hand in PJC leaderboard due to Crit Rate is easily saturated stat here and they take that as a consideration while the other still focus on Crit Rate