There are many traders who are all invested in bitcoin and altcoins, so they do not have extra funds (USDT) to buy the dip. Its not easy for everyone to see their portfolio go down and they remain emotionless. Even though we know that bitcoin prices will recover but still there is a fear of further dump which sometimes make the trader panic.
Thats why diversifying would always be the best on which you could potentially able to make possible other sources of income unlike when you do have single source.
Somehow this do really require proper financing and experience to handle it well.If not then expect the different results.It would really be depending on someones choice whether they do opt in or focus on single to have that kind of focus but honestly if you do look on bigger scale then there are lots of options to take.