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.
There is no need for miners to retire due to the halving. While reducing the block reward may make Bitcoin mining less profitable, there are still many incentives to continue mining Bitcoin, such as transaction fees and the prospect of a long-term increase in the price of Bitcoin.
Furthermore, Bitcoin miners are often large companies or groups of miners who have invested substantial sums in mining equipment and infrastructure. These individuals may have a long-term view and consider the halving as an expected event in their business strategy.