Germany during the Crusades
Interregnum (1254-1273)
The period that followed on the death of Conrad IV is called the Interregnum or even the Great Interregnum. None of Frederick's children were left, but neither did the papacy have good candidates to succeed them. William of Holland died in 1257, to be succeeded by not one but two claimants: Richard of Cornwall, and Alfonso XI of Castile. The latter did little, but Richard was fairly active in Germany.
Sicily had gone to Charles of Anjou, who spent a number of years making good his claim. The Kingdom of Italy was without any effective ruler, which naturally suited the city-states of the north quite nicely. The later 13th century was a boom time for them, but tracing the political history there is daunting.
In 1272 Richard of Cornwall died, and another election was held. The electors chose Rudolf of Habsburg (1273-1291), and this vote formally ends the Interregnum. It's sort of a funny term, since there had always been someone claiming to be emperor, but effectively there had been none since Conrad, and name has stuck.
Rudolf was just the sort of emperor the princes wanted: he left them alone. Nor did he meddle in Italy. But he made fabulously good arrangements for his family, and by the time he died the princes were worried that the Hapsburgs were become too strong. So they chose another minor prince, Adolf of Nassau.
Adolf turned out to be no weakling, however. He asserted himself right from the beginning, and almost from the beginning he was making enemies. He was deposed by a conspiracy and was killed in battle.