How are smart contracts trusted?

How do smart contracts established trusts? Is it more of a social thing - ie a lot people know that this contract from this protocol has this address, or is there a more trustless, way where someone can confirm the authenticity of a smart contracts?

I mean there are some popular smart contracts in ecosystem, from Compound, Aave, to Uniswap etc. How is their authenticity validated? Only social consensus? or something else?

What about the smart contracts that don't end up getting popular to have a good social consensus to establish authenticity? How do one trusts those?

By trust i don't mean trust that the code does what it does...but that the contract is from who it says it is from, and not someone faking/impersonating a project.