> People didn't believe what the party said,
True to some extent. However, while suspecting the party lies, they absolutely had no idea how deep and vast the lies were and that exactly was the truth. I've once heard an anecdote about North Korean woman who fled to South Korea and was asked how she thinks the life in the West is, how she thinks people in countries like USA live. She said she thinks it's a very good life, everybody is rich - everybody can get no less than 800g of rice every day!
The point is that when you live in the environment of a totalitarian state with little to no access to outside sources of information, you can easily deduct you are probably not being told the truth. It is much harder to know what the truth is, especially if you most basic assumptions might be based on the same propaganda you seemingly reject - because you've had nothing else to base them on.
And if you look at Russia now, it is surprising how many people who were alive at Soviet regime feel nostalgic about it and even about figures like Stalin. They experienced all the lies themselves, they knew those are the lies - and ask them now, they'd repeat them anyway.