Historically, there has been a number of ideas proposed. Many different variants of subchains and sidechains, different types of payment channels, ecash systems and so on.

The idea that someone discovered these in 2017 seems oblivious to what actually happened. Support for payment channels with nLockTime was likely influential for implementing transactions with smart contracts in the first place. It was there from the first Satoshi release, and payment channels was described already in 2013. It probably wasn't first on the list of things to fix as long as transactions were heavily subsidized by inflation.