When a fruit is ripe, it is time to pick it and eat it. If you say the time is ripe, then now is the time for action. Ripe means ready.
Ripe can also describe something that is not only ready to happen but well-suited for whatever is happening. A company can expect profits if the market is ripe for its product. When a ballpark has a short field, batters will say that the field is ripe for home runs. When things are ripe, it's a good thing — the time for action is now.