When Ivan I became a ruler of Moscow, Rus had already been conquered by Mongols for 80 years.
Kiev lost its political importance long before Mongols, when Andrey Bogolyubsky of Vladimir-Suzdal captured Kiev in 1149 and just went back home instead of staying to rule there. He later led the sack of Kiev in 1169, ending the Kievan Rus period.
Lords used to have flammable houses as well before they started building castles out of stone