The Bitcoin rally of 2017 was caused by Ethereum, specifically the rise of ICOs.
However, the ascent from $500 upward, which mostly happened in the entirety of 2017, was clearly caused by free money on the streets in the early ICO craze. That drove people into cryptos, mostly Ethereum as an on-ramp to ICOs, but subsequently also Bitcoin and all the others.
ICO mania really started in April, and the ETH/BTC ratio rose to its ATH in June/July. This drove a ton of hype into cryptocurrencies, and naturally every single crypto rose spectacularly. BTC would have never gotten to 10k if it wasn't for the ICO mania of Summer 2017, IMO.