"And Jesus answering said unto them, Do ye not err, because ye know not the scriptures, neither the power of God?" (Mark 12:24)
The Sadducees were a religious group in Jewish society. They were powerful, political, and wealthy. They were religious, but did not believe in angels, demons, nor life after death. What's the point of being a Sadducee? It was money, and opportunity!
So, they were wrong about a lot of things.
1) Angels do exist!
2) Demons do exist!
3) And there is life after death!
How could they be religious, and still be so wrong?
Look again at what Jesus told them. "...Do ye not err, because ye know not the scriptures, neither the power of God?"
The Bible is the believer's text book! You had better study it. There will be a test! As a matter of fact, the believer is tested every day.
Here is an example. Let's use the 'Golden Rule', which is a teaching of Jesus. 'We are to treat others as we want to be treated.' So, if someone is driving a little slower than you are, do you:
a) Tail-gate them, blowing the horn at them, and shout obscenities at them, until they either speed up, or get out of your way?
b) Patiently drive with them, because they may be looking for an address, or may not be able to see very well.
You can see how a "Pop-test" may be given at any time of the day.
The Sadducees did not study the scriptures, therefore, did not know the truth about angels, demons, and the resurrection.
So, they were, 'Sad-you-see'! Okay, that was in poor taste! I just failed a test.
Hit the Book, because there will be a test!
From my heart to your heart.