There is only one bitcoin. If you want to invest in cryptocurrencies you would be smart to look at the utility and applications of the coin you are involved with.
If people can find better alternate coin where they think that investing in that crypto will yield them better profits than they can invest in that as well because if research done proper and future holds good then one can stay invested in such coins .
Well, that's correct, I believe major investors are not only investing in bitcoin but they also invest in altcoins.
The reason is because they also believe that altcoins has a big future, the crypto market will be getting bigger and bigger as more altcoins
will be created and even if bitcoin will remain the king or the most dominant coin in the market, altcoins still has plenty of room to grow.