Our Government here will always question people who become rich instantly, sometimes they will relate all the wealth to drugs and smuggling so they can send us to jail for a questionable wealth and not paying taxes. they will do background checking, even if they dont find any illegal activities we did they still think that we do illegal. What if I become rich because of BTC do you think they will believe if I say that its bitcoin that making me rich? How will I explained to them?
The mere fact that you do not harm people and you are earning in a good way should put them to stop their accusations. Just like others said, you don't need to explain yourself, let them know what is bitcoin and how it works.