A crash of BTC wont bring down gold or anything that I can think of, maybe some digital markets could be affected.   I know BTC is quite important with parts of trading digital items sometimes, so liquidity could alter those prices.   BTC isnt mainstream currency like a main market but it would without any doubt be altered by a stock market, bond or even commodities crash.   The reason being its within the loop of 'hot money'
   The daily exchange of cheap money from low interest rate regimes like dollar or similar can reverse on a crash or change to bonds over higher risk assets.    Speculation and leverage are operative in BTC as we know there is futures, I use them daily myself to a small extent just for convenience but many would have no choice but to retract BTC long positions if margin calls forced them to raise liquidity.   It becomes a chain reaction and BTC is within that loop at least partially and its volatile enough to be taken off balance by a shift in weight even at distance.