The unemployment rate is determined by individuals filing for unemployment assistance from the government or other similar programs, such as disability. If 2 million of those individuals decided to stop looking for work, they would necessarily stop filing unemployment (active job seeking is a requirement for unemployment filing). This would, in turn, significantly reduce the unemployment rate in the country in spite of the total number of unemployed people remaining the same.
This action, while a smart decision for those 2 million people, would artificially deflate the unemployment numbers—which would look like a significant positive gain for the economy, in spite of there being no actual change. When they reentered the workforce, anyone who still could not find a job would have to reapply for unemployment, and the numbers would rise once again.