SushiSwap was created by a group of pseudonymous developers that copied the open-source code of Uniswap and added a token (SUSHI) to the design.
Their stated reason was that Uniswap was VC lead, and the market needed a DEX that was owned and led by the community.
To get liquidity fast, SushiSwap executed a vampire attack on Uniswap: it drained their liquidity by offering SUSHI tokens on top of the liquidity provider reward, but the funds had to come from Uniswap.
In response, Uniswap ended up launching their token, UNI, shortly after. While Uniswap experienced some short-term volatility, it ended up stronger.
While that was happening, the lead dev, Chef Nomi, sold a big part of the dev fund and crashed the price of SUSHI.
The community was upset, and he transferred control of the project and left. He then apologized, returned, and topped up the dev fund with the amount he had taken.
SUSHI is the fixed supply inflationary ERC20 governance token of SushiSwap.
Stakers share the profit of the platform (0.05% fee, with the other 0.25% going to the liquidity providers) and vote on things like improvement proposals, platform fees, and dev funds distribution.