Fairly simple actually, stocks don't grow exponentially after a certain point, it just isn't feasible.  XBT increased its market cap in one year by ~10B.  Which was a great feat.  But for XBT to increase 100x again, the market cap would have to increase from 10B to something with way too many zero's on it in one year.  

Can it get there eventually?  Who knows.  A LOT of factors have to fall into place for that to happen.