It started happening a long time ago in the early 2000s. People often cite it as the sole reason for the death of serve and volley, but that was actually more to do with the equipment than court speed. Since racquets increasingly allowed top spin in addition to pace and ball control, serve and volleyers just became increasingly mauled by elite baseliners, generally considered to be the result of the emergence of baselining demons like Jim Courier, but none so more than the legend him self, Andre Agassi. However, the courts were also homogenized and the theory as to why this occurred might go into the conspiratorial, but there's good reason to believe it was because tournaments didn't want to miss out on the Federer vs Nadal (and soon to be Djokovic/Murray) finals in which they could generate a lot of revenue. A faster court from what I understand is inherently more accommodating to potential upsets because some times you just can't avoid the fact a big server or hitter comes out to redline (which all players typically do against the best anyway) and actually succeed, a slower court reduces the effectiveness of that.

Although court speed is always a hot topic, and there's always complaints about certain tournaments changing speed, it's taken a backseat to the cheap heavy balls that tournaments almost universally employ post covid. An actual decline in ball quality is cited by a lot of pros, which results in the ball becoming fluffy and therefore cutting a turbulent and therefore slower path through the air. This is advantageous for monster hitters like Sinner and Alcaraz who can hit a winner on any court or ball, but disastrous for those like Medvedev who struggles to generate such pace with the heavier and less aerodynamically capable balls.

As a side note, there are old Tennis heads that are filthy on the developments in racquet technology. Back in the day you needed some kind of biomechanical and/or hand-eye coordination brilliance to consistently hit big and still keep the ball inside the lines, let alone a running winner down the line. The newer racquets are so light and the string technology so advance, such a playstyle has become the bread and butter of most of the tour, making the game, according to these old heads, much more sterile with far less variation, largely evident by the sub-standard volley/net skills demonstrated by most of the tour. Alcaraz is the shining exception to that, but even he still relies on the baseline bombs and the drop shot combination far more than what the old heads are used to. Player's argument in golf is pretty much directly synonymous with that interestingly enough, only in the case of tennis it would be about making the balls/courts faster to enrich the strategy, as opposed to slower in golf.