I don't think size really matters, It's not just an alt, it's competing with bitcoin, with intentions to take the throne and the name is similar. Market cap isn't too small either. Let's not forget there is lots of manipulation in the market and maybe whoever cares about bitcoin being always on top doesn't want to give it any chance.
They're certainly trying hard but not really getting anywhere. Check trading volumes. Today it was beaten by Bitcoin obviously, ETH was not too far off quadruple the volume, EOS was nearly double, TRON, whatever that is, wasn't too far off either.
As for transaction volumes, Litecoin and Dogecoin was double today.
It's a sizeable market but nowhere near dominant. It's not going anywhere but it has no bearing on Bitcoin's behaviour. The whole market was sucked dry by that bubble. All that's left at the moment is bots playing with each other. People will need to return for it to turn around and that might take months or years.