As we all know BITCOIN mining will stop once the 21 million mark is reached. According to the information we have 19 millions coins were mined and now circulating. The remaining balance is about 2 millions to be mined. Why it is not possible to mine the remaining BITCOINS before 2140 when the 19 millions mined in just over 10 years?
Halving is the reason mate, on every halving, the amount of bitcoin released to miners is reduced by half, so by this, I believe you should understand why it took just 10 or a little more years to mine 19 million bitcoin, but will several years for the remaining 2 million bitcoins to be mined, this is clearly because, the blockchain reduced the amount of bitcoin miners get, from now on, they are earning far lesser bitcoin than they earned 10 years back.