I think the reason for the current situation is the fact that we have a lot of new players in the game and they are not prepared to pour 10-20k in one go at the beginning. On top of that we have an element of psychology here.

When I first started investing myself I wouldn't really buy any of the big coins, because I used to think, that If I purchase let say Dash for $1k and it grows by 20% I'll have only $1200 but if I spread that 1k and buy 4-5 cheap coin in bulk for 0.05 and the price goes to 0.10 I'll have a 100% return and we've seen this in the past with Ripple, Verge and now Tron.

Smaller investors (usually newbies) prefer altcoins because they are exciting, they move a lot, BTC was up and down in last month or so but not as much, we had some big dips but in general it was't that bad.

I feel that people look at BTC and they think it's a "boring coin" they want those "fast and furious " coins that will get them "lambo" very fast. But we will see in time. My prediction is that BTC dominance will stay at around 35-45% as long as the stream of new people buying crypto will keep flowing steadily into the cryptosfere.