Different eras.. Rating inflation... Had they been playing in the same era kasparov carlsen and fischers peak rating would've been more or less the same
this means Spassky, Tal, Botvinnik, Petrossian are less memorable than all these guys? :-/ I wonder if it wouldn't be more interesting to propose an elo system cutting back your achievements every year.
The aim of this list was "The top 100 players by rating". No one is taking away from these great theoreticians but this list was only the top 100 by rating.