Because these figures are not only political leaders. They are symbols of national liberation, national pride, national self-determination and even national security. Even weak Chechen leaders become strong symbols as soon as the Russians come too close. They defend their state. That is why Pains proposal to solve the conflict is inadequate.
Pain thus treats the problem as a purely economic issue.
But the Russian-Chechen relationship is fundamentally a political problem and it can only be solved politically. A compromise must be found between the Chechens demand for self-determination and the Russian claim of great power status and respect for the principle of the territorial integrity of states.