This is likened to two people who learn a sugya in Gemara. For one person it goes swimmingly... he’s into it... but occasionally he strays from the peshat. Then there’s another person who’s quite obviously not even here. He’s simply not in the sugya.
The same applies to the sugya of Yerushalayim. There are people who are adjacent to Yiddishkeit...they perform the mitzvos that they must—but they’re not in it! They’re not in Yerushalayim. The Ribbono shel Olam asks of us a פנימיות Yiddishkeit, and when we live such a Yiddishkeit, Yerushalayim will be rebuilt.
This isn’t a segulah or something that says in a sefer—it is the essence of what it means to be a Yid: wanting Yiddishkeit for the connection to Hashem, and fearing evil because it will interrupt this kesher.
