Recently ETH got huge price increase. Is there any specific reason for that much of Increase ?

I think the reason of that rising may be the popularity. People's interest in cryptocurrencies has increased, and in my opinion, ethereum is the best altcoin.
if we take into account the prospects that the specialists predicted for the near future, then we need to have time to buy the etherium, before it's too late. The fact is that the prices practically can double already in the near future.
I agree, we all should buy etherium before the value goes up rapidly. If the value of etherium goes down, then it is a great oportunity to buy one and hold it. There are ups and down in the market and it is not impossible for the etherium to have its value go down, even with regards to its popularity and use. Bitcoin is still the powerhouse in the crypto world and etherium is the underdog. Meaning bitcoin is still the most powerful that if the value of it rises, it can affect the altcoins prices lowering them down when btc rises. Etherium is the underdog meaning has a great chance on becoming like bitcoin. So, in summarization ETH price will be unstable as long as bitcoin can rise even more.
In my opinion, ethereum is the one with the greatest potential from all stock altcoins to reach incredible prices. Maybe not in the near future, but I think it can be a good competitor of bitcoin.