It's simple: some real-world effect raises the price of a fundamental goods, such as oil or grain, which has knock-on effect on the price of doing business. This raises the price of everything.

Once the word "inflation" is on everyone's lips, the public is primed to expect price rises but have no way of knowing by how much prices will rise. This is an opportunity for corporations to find their new "price point," choosing higher and higher prices not to cover their own costs but to increase their profit margins. These companies then pass on their profits to... no one, they keep it for themselves and their shareholders, their workers just have to struggle with pay that is worth less.

This is why the rich get richer during inflationary periods while the poor get poorer.. As usual.