The last spike in 2017, $10k-$19k, is what this article refers to as „the rally. That was not caused by ICOs, but likely by a single entity (I was witnessing it in real-time back then on multiple exchanges and the price action definitely looked like one entity with ultra deep pockets was running a buying bot with no limits whatsoever - I had this theory back then already, although I got the exchange wrong, I thought the action originated from GDAX, but the paper here says Bitfinex).
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.
Yes I remember this as well, but the real rally was from 1.2k to 10k from January to November. I do remember the spike from 10k to 20k in December, and it did seem very unnatural to me, but it could have also partly been due to euphoria.
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.
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.