"The transition to a market economy in Eastern Europe and the former Soviet Union proved to be more difficult and lengthy than many economists predicted. In Moldova, the ‘side effects’ of the reforms had the worst impact on the quality of life of the population. After more than 10 years of economic experiments, the country is much poorer and more volatile than in 1991, when it gained its independence from the Soviet Union." -Moldova Foundation

This basically means that following the collapse of the Soviet Union, many countries found it difficult to switch from planned to market-based economy, and Moldova was the one that got it worse.

Besides, as it is explained on the link, Moldova failed to implement changes suggested by IFIs(International Financial Institutions), meaning that the crashed economy from 1991 saw little to no change, and sometimes that change wasn't really for the better.

To add to that, Moldova is the poorest country in Europe, and that makes investors a bit too careful in investing in it, because they think that they will not be paid back since Moldova might crash again.

I highly suggest you follow the link, as it provides many insightful views about the current economical situation in Moldova.

EDIT: Fixed broken link