Ethereum has virtually unlimited supply while BTC is capped to 21 million coins.

Out of this 18,404,300 BTC are in circulation. If you understand the basic principle of Demand and Supply then it would be easy to grasp this. The demand is heavy for bitcoin while it's supply is limited.

After each 4 years it will go under halving thus reducing its rewards per block, making it more costly to mine for minder. Since it use Energy to mine via miners, the energy required is now more and more.

This is converted into money later when people buy it.

It will keep rising since energy requirements to mine the coin will keep rising throughout the time, and also supply will keep reducing.

Moreover, you get value because investors keep buying it.