Bitcoin would give quick returns than Golden? Yes. Then why didn't they invested earlier?
Well, without any doubt. 
Bitcoin has proven itself as more profitable for investors throughout those years than gold and there's no doubt if someone invests in Bitcoin then that person will get quicker and higher profits then the ones who invest in gold. The ones who haven't invested in it earlier were skeptical and now they're investing due to FOMO.Now they know and they will be wiser next time.
Or it will be their loss indeed if they don't learn what happened during this cycle.