One donor backcasted, starting from 2021 back to 1921.
The donor compared an unconfident grant from two example funds:
(A) Maximum Impact.
or:
(B) Long-Term Future.

(A) One Fewer Minute of Deswamping

(A) In June 2021, GiveWell Maximum Impact Fund cited 3 grantees.
https://www.givewell.org/maximum-impact-fund/allocation-q1-2021

One donor's interpretation was that GiveWell felt less confident in:
Mosquito bed nets in Democratic Republic of the Congo.

In 2021, one fewer dollar to the Maximum Impact Fund might have reduced a fraction of a mosquito bed net, which might be expected to increase the risk of one case of malaria.

Backcasting 1921-2021:
In 1921, malaria killed many humans. Deswamping prevented malaria.

(B) One Fewer Minute of Speculating the Universe was Created

(B) In July 2021, EA Long-Term Future Fund cited 18 grantees.
https://funds.effectivealtruism.org/funds/payouts/july-2021-long-term-future-fund-grants

The above donor felt least confident in the following grant to protect 2121:
"Investigating implications of the simulation hypothesis."

In 2021, one fewer dollar to the fund might have reduced speculating the universe was simulated by a minute.

Backcasting 1921-2021:
In 1921, many creationists speculated the universe was simulated.

Comparing Reduced Malaria to Speculating the Universe was Simulated

By one donor's intuitive comparison:
(A) In 1921, one fewer minute deswamping felt relatively riskier to civilization in 2021.
(B) In 1921, one fewer minute speculating the universe was simulated felt relatively safer for civilization in 2021.

Stated in positive terms, the above donor felt more faith that:
one marginal dollar from 1921 protected 2021,

because someone might have:
(A) deswamped one more minute to reduce a risk of one case of malaria,
rather than because someone might have:
(B) speculated one more minute that the universe was simulated.

Caveats

The donor compared one unconfident grant of one marginal dollar.
But the donor did not arrogate how a fund manager would have cut a budget by one fewer dollar.

The donor did not forecast 2021-2121.
In the past twenty centuries, each previous century extended some trends into the following century.
1821-1921 extended some trends into 1921-2021.
Yet a model of which trends to extend into 2021-2121 felt uncertain.

What are More Examples?

Above was just one example, roughly drafted during one hour.
During a one hour draft, what would be another example of one donor comparing one marginal US dollar from 1921 to protect civilization in 2021?