I will reframe this to say Nadal's FH is very effective at exposing weak to mediocre backhands. They cannot really deflect the shot and it will keep going being easy pickings for Nadal's FH.
Nadal is also pretty effective all round against decent backhands as well. The short angle high bouncing BH can make it difficult especially for one handers to get good leverage on. Even Wawrinka will struggle because of how much weight the FH shot has driving him further out of court than he would like (and therefore unable to produce as penetrating shots in reply). The issue Federer had with their matchup before 2017 was that his BH wing was not consistently deep or targeted enough to really challenge Nadal. This was especially true at Roland Garros. You can see how Federer literally keeps playing to one side of the court, too comfortable for Nadal. From time to time, he would ramp a harder stroke deep to the corners, but few and far between.
Tsitsipas also struggles in a similar fashion (not always so obvious, but it's part of the reason he loses many tight battles with Nadal), if the BH is not targeted enough, Nadal will wring out the point.
The two hander is more stable and if used well, can give Nadal issue. Doesn't mean Nadal cannot beat them, but he has to work harder and compensate more. The trick is to make "impossible ground coverage". The best type of BH to hurt Nadal must be versatile and tidy, accurate and deceptive in presentation. Nadal may be able to counter some good ones but persistent striking to the corners including the DTL shot will make it hard for Nadal to keep up indefinitely.
I like to use Kei as an example because his 2 hander is known for its persistent accuracy towards the sidelines. Kei lost this match at AO in straight sets but the BH really made Nadal have to work, as so many FHs from Nadal that would create openings did not do the same against Nishikori, who could keep his baseline, and even if he was pushed a bit wide could often compensate with difficult balls. Three good BH points in a row...
If you watch this, you cannot really say Nadal "kills" the Nishikori BH, since that BH hurt Nadal more than the other way round, rather that Nadal won in spite of that shot.
