What is the wisdom behind sending two or more prophets at the same time, such as David and Solomon, Jesus and Zechariah and John, Moses and Aaron, Abraham and Ishmael and Isaac, and Jacob and Joseph, whereas the norm is for there to be temporal gaps between messengers?

The wisdom behind sending prophets is to establish proof against creation so that people will have no excuse on the Day of Resurrection. As for the multiplicity of messengers in a single period, it has its reasons, among them: that each prophet was sent specifically to his own people, and the messenger was sent in the language of his people, and a messenger might need assistance, and those to whom he was sent might be rebellious, thus requiring more than one messenger. Among the reasons also is the divine will for the continuity of the Sharia (definition) and its preservation from obsolescence.