The development of alternative cryptocurrencies, also known as altcoins, had both positive and negative impacts on the early adoption and growth of Bitcoin.
I disagree on this, people were rather afraid of investing with bitcoin beca of the negative role altcoins have been playing in cryptocurrency that has made many believed it's the same as a ponzi scheme whereby their asset could vanish away like a thin air, moreso bitcoin was the first introduced digital currency people want and not the other cryptocurrencies, their fate is determined by bitcoin as well.
On the positive side, the emergence of alternative cryptocurrencies helped to increase overall public interest in the concept of cryptocurrency and blockchain technology.
I still don't understand why you are so much concentrated about altcoins here on bitcoin discussion board, altcoins has nothing to offer than distractions, people on the look on how to invest with bitcoin eventually falls the hands of exchanges who introduced their altcoins they promote to them instead of bitcoin and this makes it a threat on many having this FOMO with investing further with bitcoin after having altcoins experience.