Let's analyze how easy it is.

I think it's clear that Vova had more mana (Pegasus and Berserk were used).

Let's assume a bolt is cast on the Dark Dragon right away. 6 remain.
6 Dark Dragons deal damage to the Forest.
(6x(40-50)x(25-12)x(1+0.05%))x0.85=336-420
This is 5-6 Forest units.

In response, 25-27 Forest units deal damage.
25-27x(10-14)x(1-(25-9)x0.25%)x1.3x0.85=165-192
Then, the Forest kills the 6th Dark Dragon, and the response deals about 280-350 damage (4-5 Forest units).
In the next round, there are 5 Dark Dragons against 21-23 Forest units. Our first move is another bolt on the Dark Dragon, leaving 4.
These will deal 224-280 damage (3-4 Forest units).
It's already clear that the next bolt will reduce the number of Dark Dragons to 3.

So, at the very least, it's not that simple.