I'd agree with Alice025 on her last comment.
Controller saying "MolodEts" shoud not be simply seen as praising Yak pilot performance.
For one thing, intonation is crucial - there is a way to voice it that the meaning would be just the opposite, like "crazy SOB". Easy to do it, just say it slower that usual, stretch it a bit and You are sounding sarcastic.
Or if the first syllable is stressed, like "mOlodets", it would not be praise for sure. On the contrary, it's more like scorn.
The most likely meaning in our instance though is controller's relief that a dangerous situation has turned out all right. Like "Phew, he made it!"