The other 'swords' considered were largely unenthusiastic, once Bonaparte turned up he was the obvious choice, what would have happened if he hadn't arrived at that time is anyone's guess. "All eyes were turned to him, and from thenceforward he was regarded as an anchor of hope and salvation." - Macdonald.

I doubt if anyone thought Bonaparte was not political, just that he was not firmly attached to any given party so they all tried to get him, which gave him a lot of bargaining power. Once the coup was launched there was no turning back, if it had failed there would have been no chance of the leaders escaping by sacrificing Bonaparte.
"We would all have fallen victims to the party which, to the misery of France, would have been triumphant." - Macdonald again.
I don't think the politicians realised what the price of Bonaparte's support was likely to be - I doubt if many of them intended the result of the coup to be him taking first place in the government.

Susan