There are a few potential reasons why the UNI token lost almost all of its value:

• Decline of DeFi hype – UNI is the governance token of Uniswap, a leading decentralized exchange. DeFi was hugely hyped in 2020 but interest declined since then along with UNI’s price.
• Increased competition – Several competitors like PancakeSwap, Curve Finance, Trader Joe etc emerged to take market share from Uniswap, reducing its dominance.
• Regulatory uncertainty – Increased scrutiny and potential regulation of the DeFi space by authorities undermined confidence in the future of DeFi.
• Macro environment – The broader crypto bear market and risk-off sentiment in global markets weighed heavily on speculative assets like DeFi tokens.
• Token distribution – A large portion of UNI tokens were distributed to investors, potentially causing selling pressure as they took profits.
• Lack of utility – UNI’s main utility is governance of Uniswap parameters. But this was not enough to drive sustained demand and value.
• Loss of network effects – As Uniswap clones emerged, its first-mover advantage was blunted reducing the appeal of holding UNI.

So in summary, a combination of declining interest in DeFi, increased competition, regulatory fears, and greater selling pressure led to UNI crashing from highs around $45 to under $4 currently.