I think that one of the very important reasons why we may see people dumping their alts and going back for bitcoins, is that there is not so small possibility for hard-fork to happen.
In the moment of fork, every bitcoin holder would still have his bitcoins ( BC-bitcoin core ) but also, he would gain the other bitcoins ( BU ).
That is why people dont want to miss their chance, to hop in also into BU without even big effort. All they have to do, is hold their funds stored in bitcoin,  to also jump on other ship, with different cryptocurrency.

It is not strange at all for me, after all, people want to diversify their wallets, which is a very good move for every investor/trader.