2011 Sambo Worlds final: Kurzhev vs. Papov

[DBK]

now i understand what combat sambo is lol. can someone explain to me though like in this fedor video, why do they always stand it up as soon as fedor throws the dude to the ground. Is it because its a sort of clean throw like in judo? and why do they sometimes let it stay on the ground where they can sub? ive tried looking up the rules but i havent got a clear explanation before.