On Fork: Lakes have a lifecycle to them. Newer lakes have a LOT more nutrients in them, and a lot more varied biomatter as the lake is first flooded, and there is a lot more underwater structure. After the lake has had a few years to get going, the ecosystem usually undergoes a boom for several years. As the lake matures, nutrient levels drop off some, the bottom gets silted and has less structure exposed, and the population settles into a mature cycle with stable fish populations of more average size. Sometimes if a lake is very low for a long while, and then refilled, you can re-create that youthful lake condition to an extent.
The dilution of the floridas with native genetics over time as mentioned above is probably also a factor. Native bass seem to be longer and leaner, from adaptation to living in rivers, as TX had no natural lakes...