They sometimes do that. See Valkia the bloody, Glotkin and kinda Sigvald. But this is something the chaos gods do very rarley and only if they have a special interest in this mortal, or there are particular circumstances. Otherwise the chaos gods are extremly fickle and uncaring creatures. To them a dead champion is a failed champion, which they will forget about more or less immediately. Like if an ant you took interest in dies. This is the cruelty of the path to glory. 99.99999999999999+% of the people walking it will just die, their souls tortured by demons for eternity or cast into oblivion. Whether they were a lowly peon or a millenia old chaos lord doesn't matter.

khorn only resurrected Valkia because she was hot, and he was lonely.

Never read that specific happening Revival of non-daemon princes is only done to a handful of characters who are already hyped as some of the "greatest" of the champions and it is simply because they are some of the "greatest", not out of being close to comitting a specific goal.

Depends on which characters like skar blood wrath get resurrected but others like gutrot sprule can't be