According to analytical department of the English-language Radio Liberty, the materials of which are almost never broadcast in the programs in the Russian-language service of this US government radio, there are three possibilities why the Emir Dokku Abu Usman revoked his statement about resignation from the post of head of the Caucasus Emirate.
1. He may indeed have been forced to step down by younger field commanders, who
a) are not ready to target the civilian population,
b) on the contrary, they are eager to do that but do not consider him an efficient military leader for such operations.
(Radio Liberty, evidently has in mind that new attacks did not follow in Russian heartland after the sabotage in Moscow metro although the Emir promised them for the future).
In fact, Umarov in his initial statement explained his decision to step down in terms of a need to hand over responsibility "to a younger ...