Making a Frog mostly unblockable might not help Kenrith, but if I've got Yargle and Multani, or just Yargle, Glutton of Urborg, in play, I will be well positioned to put some pressure on a tablemate's life total
It's also a fantastic fit for green in general because of green's ability to produce mana without artifacts using cards such as Llanowar Elves and other mana dorks
There's not much more to say here than I think this card is a nice way for Control to snag an early engine card from these decks, and then have room to Stock Up or Consult the Star Charts on the following turn
Conversely, if a permanent is sacrificed during the resolution of a spell or ability, that spell or ability will finish resolving before Carmen, Cruel Skymarcher's second ability is put onto the stack
They reveal the top card of their library