Valuations aren't attached to reality. Look at Crypto, NFTs, Quantum computing etc. You can have a completely non-viable money pit but if it hits the right hype cycle mix you can make huge exponential gains. It's just about what other people can be convinced to invest in. Right now the US tech sector is pretty much the only game in town to dump money and hope for huge returns. Previously it was "emerging markets" but right now there's a lot of regulatory overhead limiting gains in most EM countries.