In the 1990s a group of computer programmers and cryptographers generally called cyberpunks was working on the alternative digital currency. They were very few and working individually. Some of them came up with their model of digital currency accounting system like bit-gold was one of those projects which were infants and infamous.
After the Lehman brother collapse and when global recession broke out in 2008-09 in the United States resulting in devaluation of dollar to a significant level forced the investors and others who lost their money because of recklessly lending to corporates by banks and their politically motivated decisions to think about an alternative to dollars or any global reserve currency controlled by these third parties like government and banks.
Why do we need Bitcoin or alike?
Have you ever thought of transacting digitally without involving any third party like visas or MasterCard which are ultimately connected by banks in which you have your account? Your bank knows when and how much money you are transferring to whom.
These third parties also charge us for their services like maintaining an accounting system or money in general as they try hard to record the transaction of every penny without considering the breach of our privacy.
So after the global recession, these third parties lost their trust and those cyberpunks started working on the digital currency with more enthusiasm.