I know alot of people want to believe that. And that's the popular version for onehanded backhand proponents to believe instead of the truth, that the two hander is taught more because it is a better shot for most and better for baseliners and coaches want to teach it.
If there was any truth to your version, you would be able to explain how all the pro's in the wood racquet days were able to play with onehanded backhands with much much heavier racquets instead of referencing sampras or edberg that were one of the few that did switch but only because the coach was old school and wanted them to play a serve and volley game.
Kids being to weak to use a onehander has nothing to do with the domination of two handed players. It's the power baseline game that's played today that's superior to serve and volleyers, or onehanders trying to play baseline.
"You have to expect things of yourself before you can do them." -Michael Jordan