Probably because of the high demand
No. High demand will result in the price going higher, and thus more interesting for people to take a position into Bitcoin.
how it became hard to mine
Mining nowadays is only for people with tens of thousands of dollars that they can invest into hardware. If that's not possible for you, then please don't bother.
no one can buy it for its very high price
Current price might be on the higher side, but it's not that people can't afford themselves an investment into Bitcoin. Also, you don't have to force yourself to buy a whole coin as you simply can buy smaller fractions of a coin. Bitcoin is a divisible currency tool where you can split 1BTC into 100,000,000 smaller fractions (satoshis).
maybe possible to see other alt coins taking over probably litecoin since it is the second after it
It's not 2013 anymore where Litecoin was still seen as the Silver, where Bitcoin was the Gold that people were talking about. Right now it's all Ethereum & Co that people are interested in. Litecoin isn't part of the deal anymore. It's there, but that's all you can say about it.