It does sound quite preposterous that the Jews of all people would accept G-d’s Torah which has so many obligations. We are talking about Jews – probably the most argumentative group of people.
They didn’t know the demands, but:
- They had some inkling because there were already many traditions passed down. There was a history from Avraham, Yitzchak and Yaakov of traditions whether they kept them but most likely they were aware of them.
- They had been introduced to G-d in the most intimate, dramatic demonstration of power/love more than any people in the world ever in history or even in the future.
They were taken out of Egypt through 10 plagues that were so above nature with details that held many significant layers of meaning and then our Sages say the splitting of the sea had even more miracles than the whole year before it.
How many times have you made decisions based on what later you would realize was seemingly small jumping ground to take on obligations. (Like marriage, house buying or car purchasing). I have heard that research has proven that most people make decisions from their emotional needs, first impressions more than any concrete information – and they are not bad decisions, either.
It was really a no-brainer to trust G-d at that point; He had done so much for them – of course they would trust Him. Really the question is how did they fall so fast with the sin of the golden calf?