Rhetorical motivePrincipal basisEffect
Strong causesRobust means for realizationShows the future as close to assured
OptimismHopeful expectationConveys confidence in a good outcome
Strong desirePsychological attachment to the outcomePictures the desired event as present or achieved
All three may lead to future reference expressed through past forms. Nevertheless, their underlying reasons differ, and a correct reading should identify what the context actually supports.