so long as the other guy doesn't win

The Yalkut Shimoni writes that the news of Avraham Avinu's passing led Eisav to kerifa:

אָמַר לוֹ עֵשָׂו מַה טִּיבוֹ שֶׁל תַּבְשִׁיל זֶה, אָמַר לוֹ שֶׁמֵּת אוֹתוֹ זָקֵן. אָמַר לוֹ בְּאוֹתוֹ זָקֵן נָגְעָה מִדַּת הַדִּין, אָמַר אִם כֵּן לֹא יֵשׁ מַתַּן שָׂכָר, וְלֹא תְּחִיַּת הַמֵּתִים

If ruchniyus had no meaning for Eisav, why then did he value so much the blessing of a tzadik, his father Yitzchak?  How can you have emunas chachamim in the power of a blessing but not believe in schar v'onesh?  

R' Eliezer Kahan, the menahel of Yeshivas Gateshead, asks this question in his sichos in the sefer Nachalas Eliezer.  I'm not sure that this question is really a question, as plenty of people who are not shomer mitzvos lined up for a dollar and a bracha from the L. Rebbe.  People who don't believe in G-d still believe in a Rebbe : )  

R' Kahan answered that Eisav's belief or lack of belief was not a product of deep philosophical thought, but was motivated by his desires and appetites.  When a person is motivated by desire, then his belief is malleable depending on the whims and desires of the moment.  Serving in the mikdash was not something Eisav cared about, so he happily discarded his beliefs and gave up the bechora for a pot of soup.  When it came time to get the brachos, the promise of reward led Eisav to put his trust in the brachos of his father in order to reap that bounty.

I think one can perhaps draw another distinction.  The butcher of Brisk once came to R' Chaim to pasken a shayla on his cow and R' Chaim declared the animal a treifa.  This was a considerable loss for the butcher, but he took the news with equinimity.  When R' Chaim on another occassion paskened against this same butcher in a dinei mamonos dispute with his neighbor, the butcher raged against the psak and hurled invectives against R' Chaim.  This was a much smaller loss than that of the cow, so why was the butcher so upset?  The answer is that it is not the loss which bothered him -- it's the fact that someone else won.   

When it came to the sale of the bechora, Eisav weighed the gain of a pot of soup against what he thought was the meaningless value of bechora, service in the Mikdash, and he did not feel cheated in any way by the deal.  In fact, he though he got the better end of the deal, as R' Dovid Tzvi Hoffman comments:

ויאכל... ויבז – במלים ברורות מראה הכתוב שלא ידע עשו להעריך נכס רוחני, ושכל שאיפתו לאכילה ולשתיה היתה מכוונת, כך שאפילו אחר שאכל לשבעו, לא התחרט על המכירה הזאת. אדרבה, חשב שעשה כאן ״עסק טוב״, כי אכן מעיד הכתוב – ״ויקם וילך״

It was, in Eisav's eyes, a fair transaction.

The same cannot be said about the loss of the brachos.  Here, Eisav did not see the link between the bechora and the brachos and thought that Yaakov took what was rightfully his.  Even if the brachos meant little to Eisav, it's the fact that Yaakov won, the fact that he was bested, which drove him mad. 

We see similar behavior from the Plishtim elsewhere in our parsha (26:18):  

וַיָּ֨שׇׁב יִצְחָ֜ק וַיַּחְפֹּ֣ר׀ אֶת⁠־בְּאֵרֹ֣ת הַמַּ֗יִם אֲשֶׁ֤ר חָֽפְרוּ֙ בִּימֵי֙ אַבְרָהָ֣ם אָבִ֔יו וַיְסַתְּמ֣וּם פְּלִשְׁתִּ֔ים אַחֲרֵ֖י מ֣וֹת אַבְרָהָ֑ם

Stealing the water of wells is understandable, but why stuff up the wells?!  Water is a valuable commodity in the hot climate of Israel.

I recently heard a shiur by the new chief Rabbi Kalman Ber in which he suggested that what motivated the Plishtim was ensuring that the other guy loses.  It didn't matter that they had no water -- so long as the other guy didn't get any either.  This is their attitude ad ha'yom ha'zeh.  It's not enough for them to have a state -- they could have negotiated for that many times.  What bothers them is that we have one.  Therefore, they can never be satisfied and will never achieve their goal.