This is not an effort to reduce the status of any player.ok?
Ok. My answer is: Who knows for sure?
Clearly she was under intense pressure from the German press, which always suffocated both her and Boris Becker. I'm sketchy on details and timeline.
Something was up with Graf as early as early 1990, when she looked listless in the Aussie. (the book Hard Courts goes into more details).
The Nicole Meissner thing must have been a shock, but when did she know? Was it when the press broke the story or before?
When did her parents separate?
And tough as all that was to take, to me her father going to jail for tax evasion would have been even tougher. That's me though-heck, by that time one hopes Steffi had on some thick armor to protect her emotionally.
All of these things surely had a negative impact on her tennis and contributed to the "slump" some talk about in the early 90s.
I don't think it makes Steffi unique among tennis stars though. Evert and Navratilova had their own personal/public traumas which affected their tennis. Doubtless all tennis players do.
Personally I still think Seles would have had the game in her grip, Monica was just that good IMO.
But who knows-had Steffi been able to win the German or French over Seles in 1990 things might have been different.