How could they not know the consequences, when God had already spelled it out? "Thou shalt surely die" was plainly stated.
Indeed it was. But Eve believed the serpent, "ye shall not surely die". And there were more consequences to their sin than death. The world became cursed, animal nature changed, the ground became cursed, thorns and thistles, childbearing became painful, and more.
Eve chose to be deceived. Yes she was deceived but she chose to listen to Satan, and also chose to deceive herself. She knew the commandment but altered the words so that she could go ahead and disobey God.
People do not choose to be deceived. That's part of the meaning of deception. Yes, Eve changed what God had actually said, added words "neither shall ye touch it", and so forth. She should have stood firm. But she didn't. She was deceived into listening to the devil, deceived into disobedience.
Let's take an example closer to home. Right now President Donald Trump is doing an outstanding job to put America first and to make America great again. Yet there is NOT A SINGLE LEFT-LIBERAL who has commended Trump for his efforts and his achievements. They have chosen to be self-deceived and instead have called him every vile name you can think of.
People may BE deceived, but people do not choose to be deceived.
Hey, I'm a pretty far right leaning conservative who voted for Trump. And I agree that the media is for the most part TOTALLY against him and everything he does. They always present everything he does in the worst possible light.
That said, Trump is not without issues...