Why did Yitzchok use the same subterfuge for his wife that had not worked for Avraham?

Question

When I read the Parashas Toldos, I was surprised to see that when Yitzchok went to the land of Avimeleh, he said that Rivka was his sister to protect his life in Bereshis, 26, 7.

It is obvious that he knew that Avraham had used this trick in Egypt, claiming that Sarah was his sister. We know what happened at the end: Sarah was taken by Pharoh. Yes, Avraham's life was saved. But what about Sarah's life and integrity? Thus, we can consider that this trick was a failure.

In this case, why did Yitzchok use the same lie in a similar situation?

In the end, Avimelech also discovered that Rivka was not his sister either ...

Or maybe, that the Torah considers that the trick used by Avraham was not a failure? Indeed, Avraham had told Sarah that she had to say that she was his sister so that "we would do him good, thanks to her" and then "his life will be saved" in Bereshis, 12, 13. Now, it seems to me that the Torah stresses in a somewhat ironic way that this is exactly what happened: Avraham received many gifts as Sarah's brother in Bereshis, 12, 16. Subsidiarily, Sarah was held at Pharoh's palace ....

Answer 1

The subterfuge was actually successful. Yitzchak was afraid of the people of the country and the trick worked until they had been there for long enough to get careless and get caught.

Toldos 26:7 - 11

7 And the men of the place asked about his wife, and he said, "She is my sister," because he was afraid to say, "[She is] my wife," [because he said,] "Lest the men of the place kill me because of Rebecca, for she is of comely appearance."

11 And Abimelech commanded all the people, saying, "Whoever touches this man or his wife shall be put to death."

As Rav Hirsch says:

That Isaac's precaution was not without cause is proved by the fact that, once the true relation between Rebecca and Isaac became known, Avimelech found it necessary to protect them by a decree of the death penalty for any assault.

Note that the trick that Avraham used was also successful with respect to all the nobles of the country. It was only Par'o who actually took her because he was above the law and did not have to court Avraham to try to get to Sarah. Similarly Avimelech castigated Yitzchak saying:

10 And Abimelech said, "What have you done to us? The most prominent of the people might easily have lain with your wife, and you would have brought guilt upon us."

Rashi

The most prominent of the people: Heb. אַחַד הָעָם, the most prominent one of the people, meaning the king. [Gen. Targum Onkelos and Jonathan]

Only the king would have dared take her. Everyone else was stopped by the trick.