In other words, you implicitly assume that Bitcoin reached an ATH due to altcoins emerging en masse, right? Or, put differently, if it weren't for altcoins, Bitcoin wouldn't reach so high a price in 2017?
You are right, I was thinking of that and I believe it was Altcoins which makes bitcoin reach its ATH.
The thing is, when that time there's a lot of running ICO, they invested on it as ICO that time are so profitable, but then its just normal for risk management purpose that the team who own a project in ICO would raise BTC and ETH as these two coins are more stable compared to the others and even some have converted their ETH for bitcoin, so btc's demand increases.
If anything, I think it is quite the other way around. For example, if there hadn't been a split which led to the creation of Bitcoin Cash, Bitcoin would have reached even a higher price by the end of 2017
Not sure I would agree with you on this because when I say altcoins, I am referring to majority of coins that are created through ICO.