Young bass need a place in which to hide from predators and from which they can feed upon the near-microscopic forage they require as fingerlings. In lakes with fairly consistent water levels, this is no problem. As spring arrives, aquatic vegetation grows easily and rapidly along the shorelines of most lakes. Just-hatched fish move into those vegetated areas, with most remaining there until they grow large enough to survive in the open. Such vegetation and other cover needed by young bass are generally absent in lakes with falling water levels.
Any aquatic vegetation attempting to grow in the shallows soon is left high, dry and dead.
With little cover to protect and nurture the young bass, mortality from predators can be incredibly high. A ton of rain probably would not help things that much, just now. Any big rises in lake levels right here in the middle of the bass spawn could negatively impact recruitment as much as continuing drops in water levels. That's because the shallower water warms quicker, and that warm water is necessary for the eggs to hatch. If a lake level jumps several feet, it could put nests in water too deep and too cold for success.