The question you asked is "why is it important to remember historical events?"
The answer to your question is simply that in order to stop bad things from happening in the future, we must learn from the past.
The holocaust is one example of something we don't want to repeat in the future, therefore we must study how Hitler took over Germany. A few of the things he did was took over the school systems so that he could indoctrinate the children. These children became known as the Hitler Youth. Another thing he did was take away guns from Jewish people so that they could not fight back.
If we realize what Hitler did to take over, we can stop fascist politicians in modern day times.
The river flowed one way while the wind blew the other way which made sailing easier. If you wanted to go upstream you lowered the sails. If you wanted to go downstream you raised the sails