The one handed backhand did not lose on aesthetics

Its decline is a specific mechanical problem with high balls, and it explains exactly which players still succeed with it.

The one hander is discussed as though it were a matter of taste, a beautiful thing being squeezed out by an ugly efficient world. That framing is wrong and it obscures a clean mechanical explanation.

A two handed backhand has a second arm behind the racquet. That arm can push through a ball at almost any height, and above the shoulder it can pull the racquet across with real force while the wrists stay locked. A one hander at that height has to hold the racquet steady against the impact with a single arm working at a poor angle, with the shoulder near the end of its comfortable range. It is not impossible. It is much harder, and the margin for error narrows sharply.

Now consider what changed about incoming balls. Polyester strings and modern topspin technique mean the average rally ball bounces higher than it did a generation ago, and slow high bouncing hard courts have become the majority surface on the calendar. The one hander did not get worse. The ball it has to handle got higher, several times a rally, on most of the tour.

Which produces a very specific pattern of survival. The players who still make it work at the top tend to be tall, which lowers the effective contact height, and they tend to take the ball early on the rise so they meet it before it climbs into trouble. Taking it on the rise requires exceptional timing and gives the player less time, but it moves contact into the range where the single arm is strong. It is a technical answer to a technical problem, not a stylistic preference.

The compensations are worth having, which is why it has not vanished. Greater reach on the wide ball, a natural transition into the slice with the same grip and the same shoulder turn, easier disguise, and a better platform for coming forward. A one hander who slices well has two shots from one preparation, and a two hander effectively has to switch grips to slice at all.

So it is a trade that depends on the surface diet. On grass and fast low courts it is close to even. On slow high bouncing courts it is a losing position.

Nobody chose that trade for aesthetic reasons. The calendar chose it for them.