He said that Rav Yisrael when he was first Rabbi in frankfurt (i think, though it could have been prague?) it was known that the Jews would open their stores on Shabbat. He didn't try to fight with them to change this, instead he suggested in a modest way that since they anyways would be opening their shops the next morning, perhaps they could arrange a hiding place by the shop where they could hide the key so that they shouldn't have to carry the key to and from the shop on Shabbath. In that way they would at least avoid transgressing the issur of carrying on Shabbath.A couple of weeks after Rav Immanuel told me this story he was relating how the Gemara explains that in the time of Nechemia,(?) the Jews in Israel, even those of Yerushalayim were not keeping the Shabbath. What did the Sages do? they enacted a decree that carrying all but three specific objects was completely forebidden on Shabbath. Those three devices were minor utensils used to eat, objects which were never normally taken out of the house. Once they saw that Israel was doing teshuvah and started to properly observe the Shabbath and the decree, then they started to relax the prohibition until we arrived at the hilchoth of tiltul (carrying) that we have to this day.
The Jews were happy to comply since this was such a simple request, but what came about from this is hard to imagine. The next week they decided they would close their stores a little bit earlier so that they could spend more time at home and enjoy the Shabbath meal in a more relaxed manner. Eventually they decided to close up in time for Shabbath since it was so nice to be able to relax and enjoy the Shabbath. They would still open the next day, Shabbath day, however. Slowly the opening time of Shabbath day was pushed back as they decided to spend more time in Shul and with their families, eventually they realised they didn't even need to open in the afternoon and lo and behold the whole community, in a matter of weeks was keeping all of Shabbath and became an observant community under the great wisdom of Rav Yisrael.
It seems to me the two stories are very connected, and it actually makes plain to us how thoroughly connected the mitzwah prohibiting tiltul (muktzeh) on Shabbath is. From this one simple Rabbinic enactment entire communities of Am Yisrael have grown to complete Shabbath observance.
What is interesting is the difference in the dynamics in the days of Nechemiah, they first outlawed everything and then gradually relaxed the restrictions, in the story with Rav Yisrael Salanter, he only prohibited something very inconsequential and the people grew to complete observance on their own.
I don't know what precisely the lesson here is, but it is clear that allowing Jews to taste the sweetness of Shabbath has a profound change on those Jewish Neshamoth.