People are dying, and many of them are innocent babies... I am saddened that this is a topic related to war...
This isn't the first time that there was a kind of this bet.
IIRC, there was also a bet related to Ukraine and Russia war before and all of the other war related bets.
While we're saddened by this, bookies like polymarket will not stop in allowing these things.
I have no idea why people are betting for this, it's like wishing the bigger war to happen.
That's the meta nowadays, as long as there is something to bet for and there is a demand, it will be listed.