Many a times we have seen both the symbols looks similar. There is only one difference, the direction of the symbol. The Swastik symbol is in standing position whereas the Nazi symbol is lil bil tilted and standing on one of its corner. Now the question is why these two symbols are looking similar? The Swastik symbol is associated with Hindu religion and known for holy activities and peace where the Nazi symbol was adopted by Hitler and was a sign of mass killings and destruction. So, nature wise both the symbols are opposite to each other.
By the beginning of the 19th Century there was a huge fad for the swastika as a benign good luck symbol. And in the starting of 19th century, there are examples that shows how the western countries started using swastik in their daily products.
"Coca-Cola used it. Carlsberg used it on their beer bottles. The Boy Scouts adopted it and the Girls' Club of America called their magazine Swastika. They would even send out swastika badges to their young readers as a prize for selling copies of the magazine," - US graphic design writer Steven Heller
It was used by American military units during World War One and it could be seen on RAF planes as late as 1939.
When Germans started translating Indian Vedas in Sanskrit, they found a big similartiy in their language and in the Sanskrit, with that they'd found some similarities between Indian and German culture as well and thus they reached to the decision that there must be somewhere Indians and Germans are sharing their ancestory and imagined a race of white god-like warriors they called Aryans.
"For the Jewish people the swastika is a symbol of fear, of suppression, and of extermination. It's a symbol that we will never ever be able to change," says 93-year-old Holocaust survivor Freddie Knoller.
"If they put the swastika on gravestones or synagogues, it puts a fear into us. Surely it shouldn't happen again."
In reality, Swastik is more ancient than we think, it is not limited to only India. It was found in the ancient scriptures of Europe, it was used by ancient Greeks, anglo-saxons and some of the old civilizations. The Ancient Greeks also used swastik to decorate their pots and vases.
Now the main question - "Why did the Nazis hijack the Swastik symbol?"
So, the swastika has a long history and this symbol is using going back thousands and thousands of years to the Iron and Bronze ages. After different discoveries of Swastik in Europe and especially in Germany, they started to believe that its a common symbol of good luck in Europe and abroad.
Hitler wrote in Mein Kampf that the Nazis’ emblem needed to be both a “symbol of our own struggle” and “effective as a large poster,” and the swastika, as the nationalist movements were using it, fit the bill.
The Nazis officially adopted a red flag with a white circle and black swastika in 1920. Hitler wrote of the flag (emphasis mine),
“We National Socialists regarded our flag as being the embodiment of our party programme. The red expressed the social thought underlying the movement. White the national thought. And the swastika signified the mission allotted to us—the struggle for the victory of Aryan mankind and at the same time the triumph of the ideal of creative work which is in itself and always will be anti-Semitic.”
After millions of people were systematically killed under swastika flags by men wearing swastikas on their uniforms, the symbol become one of genocide, fascism, and racism, and any other connotations it might have had were lost in the West.