There are many factors that make altcoins experience a very sharp decline. This decline occurred when it came in in 2018, that the Altcoin slowly declined. According to my analysis that the factors influencing the destruction of Altcoins are:

1) Scams happening everywhere, they create fake ICO projects to make money in a deceptive manner.
2) greedy in trading and people investing in panic when the situation changes.

But we also have to think positively that the crypto situation will certainly not always succeed. But will have a time of trouble.
Now new hope to enter the year 2019, that with increasing Bitcoin will have a positive impact on the altcoins.