Australia defied the oddsmakers and established itself as a surprise frontrunner at the Eurovision semifinal Thursday while a trio of past winners — including 2024 champion Switzerland — failed to advance. Switzerland joined Latvia and Luxembourg as erstwhile title-holders who won’t have the chance to grab another Eurovision crown as the final 25 nations were set for the weekend’s big singing showdown in Vienna. The 70th-annual homage to soaring and sometimes silly song production will anoint a winner Saturday, ending a months-long saga that saw five countries boycott over the inclusion of Israel. The Middle Eastern nation had not broken any rules, but its presence in the competition prompted Spain, Slovenia, Ireland, Iceland and the Netherlands not to compete as a protest over Israel’s military actions in Gaza and Lebanon. Israel earlier in the week advanced to the final in the first of two semifinals.…