While a lot of the people rushing into bitcoin at the moment have no clue what's going on, and are just chasing a quick buck, there's a steadily growing user base of bitcoin providing a base for each time the value crashes back down again.
More and more people are getting fed up with the Yuan, Yen and the US Dollar losing value, and are looking for alternatives to put their cash into.
Gold and silver is being suppressed by manipulation via paper contracts and naked short selling. The gold/silver market is a 10 TRILLION USD market, while bitcoin and alternative coins have a total market cap of around 70 BILLION USD (was over 80 before prices started going down recently, and previously it was only about 10 BILLION before the rally this month).
So, if only a small percentage of the people who are into the gold/silver markets start moving into Bitcoin instead, it can make a huge impact on the total market cap of bitcoin and keep driving the price up. If the dollar keeps falling in value and losing trust, and Bitcoin keeps being used more in Japan and other countries, alongside Ethereum and other coins that are used for more than just currency, the price will respond accordingly.
Maybe bitcoin will settle around $1000-1200 this time around according to some experts. There's also the issue of the number of transactions per second being limited to 7 currently. It's being working on and this problem could possibly be solved sometime in 2017.
I recommend this video by Renegade Investor for more info and charts even if it was made before the current bubble:
I also recommend checking out this channel called Tommy World Power:
https://www.youtube.com/user/Tommy77724