the main reason was thats the more people started using bitcoin , many transactions have been done due to which it demand increased and bitcoin got a sharp rise in its value

Firstly, at one point it reached $19800 on most exchanges and even a bit more in some Korean exchanges. I would classify what we had in 2017 as FOMO rush, while seeing lot of new investors who heard how bitcoin have made a lot of early adopters rich and thought it would make them rich overnight, coupled with a lot of bullish predictions, which made missing out not an option for them.

More people started to invest on bitcoins on 2017 thats why there is a great jump in the bitcoin price.But it jumped too much in my opinion now the price correction occurred and the price if getting stable between $12K.

there is always an increasing adoption of bitcoin which is constantly contributing to the long term rise of bitcoin price. last year this adoption was "booming" which is why the price also "boomed".
here are major incidents that contributed to this big rise:

• mainstream adoption of bitcoin in Japan. finally Japanese decided to officially accept bitcoin as a "legal method of payment" and that was a big move helping the rise a lot. mainly because of hundreds of merchants in Japan that started accepting bitcoin. this was also led to change of views in other countries even in Russia after years of negativity against bitcoin.
• removal of  taxes on bitcoin payments. again in Japan and a couple of other countries like Australia. and you can imagine how merchants that were already accepting bitcoin and the new ones felt. which helps with the adoption.
• the end of 3 year scaling debate in August. finally the scaling debate which was a very big slow down for bitcoin's growth came to an end when the big blockers forked off and bitcoin could finally come to consensus and have Seregated Witness activated which also opened up lots of future possibilities such as Lightning Network, Cross Chain Transactions (Atomic Swap), more anonymity (Confidential Transactions), ...
• price rise itself. when bitcoin performs well and it is rising and giving a lot of profit, a lot of new investors become aware of it and start investing in it in order not to "miss the boat"
• a lot of publicity in the media which is practically advertising bitcoin!

The simple reasons are that : (1)the world is beginning to accept new technology or that technology is beginning to pierce into human space.
(2) That, in 2017 , we started witnessing the growth of blockchain technology.
(3) As at February/march , when bitcoin was still around $900 to $1000 dollars, we had people realizing bitcoin as a means of payment in option to fiat.
(4) There began a tremendous awareness and growth of cryptocurrency sometime around June, then bitcoin got close to $4,500 $5000.

In other words,  the growth of bitcoin wasn't just a festive celebration or Christmas awareness rather I see it that, it was and is as a result of the awareness of another means of money called digital currency or better known by others as cryptocurrency or cryptos.

As we know therefore, bitcoin is the first and has started a bullish journey already, it had no choice than to touch the all time high of $20,000 plus, stringing some good profit to the optimist, disciplines and believers of the coin (some lucky pessimist would have been lucky though )  

To disabuse our mind that the growth of bitcoin wasn't just a festive awareness but the awareness of digital currency, that is why we have not seen the coin crashing. After all, Christmas has gone.

In december it reached 19.700k at one point

1. Blockchain technology is being accepted by more people around the world.
2. Due to increased awarness people are attracted to invest in it.
3. Also, the easy access to trade and secure transactions.

I think the main reason of the rising its price in 2017 was hype around Bitcoin! I think about Bitcoin were told everywhere and by everybody. The mass media made a big contribution to the hype.

the reason that btc skyrocketed is because, many countries and companies and organizations slowly recognizes bitcoins and many transactions are made using bitcoins, specially because December is a Christmas season. So yeah, and I hope btc prices will grow bigger.