difference is because it is wrong to assume that numeric values would equal. They are different poold with different constitution of players. Very strong players do not play classic here (which does not classify as classic but lihess classic) . same goes for rapid to lesser degeree
Because there is constant flow of player entering pooll and leaving it median rating in pool will drift towards 1500. and strong players play here blitz for sure but not rapid which means that players in rapid pool are on average weaker i.e median still will be 1500 and it takes less skill to reach same rating as in blitz.
if look on weekly player of classic
https://lichess.org/stat/rating/distribution/classical only about 50 000 weekly players who played at least one game
https://lichess.org/stat/rating/distribution/blitz with dash over half million players weekly.
Havent played classical lately but I have won games on 2000+ player dropping queen just by putting on square that it can be hit. I do doubt 2000 blitz player would do it even at blitz speed or at least it must be rare. and Ido it on any speed
So tenfold amount players. rapid is about half of blitz
ten comes the personal differences. I cannot play bullet. My brains just dont work that fast nor I am fast enough mouse user. Then some people play classical/rapid at the same rate they play blitz and some allways end up in time trouble toward end. guess which one gaind on extra time available.
Probably there are even pools within pools i.e 3min players are to a degree different from 5 min players. and since I¨ve seen strong player mostly playing 3 min. it is possile that with same rating 3min players a tad stronger. And I cannot play 3 min just too fast.
