no hishtadlus required

 וְהָיָה אִם⁠ שָׁמוֹעַ תִּשְׁמַע בְּקוֹל ה׳ אֱלֹקיךָ לִשְׁמֹר לַעֲשׂוֹת אֶת⁠ כׇּל⁠ מִצְוֺתָיו אֲשֶׁר אָנֹכִי מְצַוְּךָ הַיּוֹם וּנְתָנְךָ ה׳ אֱלֹקיךָ עֶלְיוֹן עַל כׇּל⁠גּוֹיֵי הָאָרֶץ. וּבָאוּ עָלֶיךָ כׇּל⁠ הַבְּרָכוֹת הָאֵלֶּה וְהִשִּׂיגֻךָ כִּי תִשְׁמַע בְּקוֹל ה׳ אֱלֹקיךָ (28:1-2) 

Why do the brachos have to catch up to you, הִשִּׂיגֻךָ?  Would a person run away from bracha so that it has to chase after him?

There is a machkokes Ramban and other Rishonim whether bitachon requires hishtadlus or whether one can just trust in Hashem and that alone is enough, if done properly, to see that one's needs are met.  One can reconcile the two views by positing that the need for hishtadlus is inversely proportional to the degree of bitachon.  Someone who is a bona fide tzadik can sit back and trust that G-d will provide all their needs without their having to lift a finger.  Most of us are not on that level and feel that we must do something active to get results in olam ha'zeh, so Hashem responds in kind by giving us what we need only if we put in hishtadlus.  

Seforno explains our pasuk:  והשיגך – אף על פי שלא תשתדל אתה להשיגם.  Even though normally you make hishtadlus for your needs, the Torah here is promising bracha even where you make no effort and not hishtadlus to attain it.  The bracha will come to you; you don't have to make an effort to acquire it (see Divrei Siach of RCK).

2) Netziv notes that the parsha starts with the condition הָיָה אִם⁠ שָׁמוֹעַ תִּשְׁמַע בְּקוֹל ה׳ אֱלֹקיךָ.  Why does the second pasuk reiterate that this blessing is only  כִּי תִשְׁמַע בְּקוֹל ה׳ אֱלֹקיךָ?  

For some people getting a luxury car, going on a cruise, going out to eat in a fancy restaurant, etc. are things that get their heart pumping.  This is what they consider bracha.  For a person whose life is the 4 amos of halacha, these are little, meaningless things.  Can you imagine a gadol -- choose whichever one you like -- having a taavah for such things?  There was a restaurant review of a new place that opened in our neighborhood that touted the five types of cocktails that the reviewer ordered.  What a bracha!  Not one, but five options, and that did not exhaust the menu.  I don't think a cocktail menu would (or should) make a roshem on someone steeped in learning.

That being said, sometimes the olam ha'zeh bracha is so great that even someone who is immersed completely in learning will lift their head and take note.  That, says the Netziv, is the type bracha the pasuk is talking about. וְהִשִּׂיגֻךָ כִּי תִשְׁמַע בְּקוֹל ה׳ אֱלֹקיךָ : even if you are immersed completely in the dvar Hashem, כִּי תִשְׁמַע בְּקוֹל ה׳ אֱלֹקיךָ , and you take no note of such petty things as the cocktail menu or the new car or the new restaurant, והשיגך, there will be bracha so big that it will even grab your attention.