[CryptoPunk]

It's effectively porting BTC to Ethereum, given the value of the BTC can be utilized on Ethereum by the tokenized claim on BTC.

And there are wrapped BTC tokens on Ethereum that utilize cryptoeconomic incentives instead of the reputation of a custodian to guarantee redeemability for BTC: renBTC and tBTC.

WBTC was just the first to launch so has the largest market cap. It's also possible that WBTC's reliance on a trusted third party is perceived as less risky than reliance on novel cryptoeconomic incentive schemes.