Counterfactual reasoning is a practice that is very frequently resorted to in everyday life as well as in serious analysis of historical outcomes. However widespread and indeed indispensable, counterfactual analysis is recognized to be a very weak, problematical method because of its conjecture of possible alternative actions. More disciplined uses of counterfactual reasoning evaluate historical events carefully to distinguish highly plausible from implausible or barely plausible claims for alternative historical outcomes.
Counterfactuals are a way of rewriting history (exploring the possibility of an alternative outcome) by conducting a mental experiment -- i.e., "if only this rather than that had been done, the outcome would have been quite different." Some counterfactual assertions are more plausible than others.
To construct a good counterfactual analysis one needs to start with a good explanation of the actual outcome of the case at hand. This step is important, obviously, because the counterfactual changes what are thought to be the critical variable(s) that presumably accounted for the historical outcome. If one has an erroneous/unsatisfactory explanation for it, then the counterfactual analysis that argues that a better outcome was possible, "if only...," is likely to be flawed. Both the historical explanation and the counterfactually derived alternative to it are likely to be more correct or plausible if they are supported by relevant generalizations (and theory).