Continuing the aside: yes, you might split the marginal dollar because of uncertainty, like playing a mixed strategy. Alternatively, you might have strongly diminishing returns, so that you go all-in on one intervention for a certain amount of funding until the marginal EV drops below that of the next best intervention, at which point you switch to funding that one; this also results in diversification.
Continuing the aside: yes, you might split the marginal dollar because of uncertainty, like playing a mixed strategy. Alternatively, you might have strongly diminishing returns, so that you go all-in on one intervention for a certain amount of funding until the marginal EV drops below that of the next best intervention, at which point you switch to funding that one; this also results in diversification.