This is the answer which resonates most with me. The current government has long since run out of steam, and it must now be clear to them that they are going to

This is the answer which resonates most with me. The current government has long since run out of steam, and it must now be clear to them that they are going to lose the election. If they bow out in July, then they're pretty much guaranteed to be the official opposition (albeit with a much reduced majority) which gives them time to regroup and try again in 2029. If they hang on until January 2025 then there's a small -- but real -- risk that the defeat is so bad that the Tory party effectively ceases to exist.