Bitcoin is only volatile in the short term as it goes through price discovery.

Consider the value of everything in the world.

The value of everything. This is the whole pie and all currencies, fiat or bitcoin, compete to represent portions of this pie.

Assume for a second there is only one usd world currency. As more usd are printed, the number of dollars in this world increases therefore the amount of value each dollar represents decreases naturally over time. This is inflation.

Now assume for a second there is only bitcoin. Bitcoin is fixed at 21m supply so in reality, bitcoin can only be lost and the global supply of bitcoin can only decrease. Therefore the total number of bitcoin representing everything in the world can only decrease. On a per bitcoin basis, value each bitcoin represents can only go up. This is deflation.

Now in the reality of multiple currencies, when pricing bitcoin against usd... if the price of usd is forever trending down, and the price of bitcoin forever trends up, given a long time frame... bitcoin is up only. Short term volatility is just that. Bitciin is the best long term play. It's simple economics.