Here is the conclusion which they should have reached, the conclusion which they resisted with all their being. What they had witnessed was a miracle which could only be accomplished by the power of God.
What strange and hard to believe things human beings tell themselves in their effort to avoid faith in God. The whole business of idolatry is a demonstration of this. They sense the imperative of faith, but they know that they do not want to believe. Faith must therefore be dismissed with force. It is not enough just to turn away from God; unbelief has to be justified, and therefore they latch onto a counter-belief which they claim is more plausible. But it is a lie, and deep down they know it. God presents his evidence to us in a way that removes any reasonable doubt, so that any remaining doubt is without excuse. In doing this God does not at first make his evidence so clear that it cannot be resisted; he leaves room for unbelief, so that man can show how stubborn he is. To show the perversity of the human heart the Lord leaves room for fallen human beings to concoct their own explanations, but they are utterly unconvincing. We are supposed to seek after him, and to pay great attentions to every possible help to understanding which is available to us, but instead we do the opposite. We ought to so long for God that even the slightest clue to his majesty and power should be given the utmost attention, but instead we fight against all his evidence. We struggle and strive to find reasons not to believe in God.
The believer wants to reach the point of full assurance. God has given us all that we need to reach that point, but there is work to be done. We must use the minds he has given us, and we must use them in an honest way. Faith is indeed given at the new birth in abundance, but it has to be maintained, and this is done by our reflecting much on what God has told us in his word. Faith is seen to be a most reasonable response to what God has said.