The vedic scriptures define a root cause of all forms of suffering, this means, whenever you see suffering, it is caused by this one thing only and this one origin of suffering is: Ignorance.
The reason why this is should be obvious to all non ignorant people, because the universe works according to laws, if you know those laws and obey them, you can live in harmony with the universe, but if you ignore them, meaning ignoring reality, you will become insane and cause suffering to others and yourself.
Ignorance is one of the three gunas that exist as forces in the universe that drive all life. The three gunas are: knowledge/virtue, passion and ignorance/darkness. Knowledge/virtue is the best guna you can be in, since it is all perfect and will cause only joy, passion however is a mix between knowledge and ignorance and is in general the state most people are in this world and it will cause a mix between joy and suffering and ignorance is the antithesis to knowledge and will cause only suffering.
There can be some form of "joy" in the mood of ignorance, but this is all based on illusion, since there is no real joy in ignorance. The only way to get joy out of ignorance is to ignore the fact that there is no joy in ignorance.
Another main part of why ignorance causes suffering is, because it ignores the needs of other living beings. Ignorance enables someone to do bad things to others, but no matter if a person can temporary get away with their crimes, it will still cause suffering, since you cannot be truly happy, if living beings around you are unhappy, everything is connected. The reason I previously wrote temporary getting away with crimes is because there is a karma system and you never truly get away with anything, you will always pay the price for your actions, this is called karma. The guna system also helps you to deduce yourself what the karma of your actions will be, since you now know that ignorance will always cause suffering in one way or the other, there is no getting away from the laws of the universe.