It just means people are generally bullish and think the price is going to rise again soon so the demand to borrow USD and find a good spot to go long is very high. The opposite happened when we fell from 800 to 340. The demand to borrow BTC was at an all time high back then and people were generally bearish. Of course this can't go on forever and at some point the tide will turn again but this fact tells us nothing when this is going to happen so this is neither bullish or bearish.