I don't know why they did this, but Hamechadesh says that a group of the donors tracked the shiach of the kupa and saw that because of the heat, on the long walk to the grave he took his hat and jacket off. The young man fulfilled his task by saying some tehillim by the grave and saying the names of the donors, but he did so without donning his hat and jacket.

the donors asked Rav Mendel Shafran if they deserve their money back as they had expected a rav of some sort to be sent, not a bachur [who would take off his hat and jacket]. The Kupa responded that they never promised or insinuated that they would be sending a rav, just that they would send a messenger to daven and say the names of the donors at the grave - that was done and they need to pay their commitment.  

The group of rabbonim led by Rav Shafran, including Rav Yaakov Chaim Sofer, Rav Shafran, Rav Naftali Nussbaum and Rav Fried, rejected the claim of the donors. They decided that if the kupa did not explicitly promise to send a rabbi or a notable talmid chacham to daven on their behalf, sending any frum, Torah-observant Jew, is acceptable. Rav Chaim Kanievsky agreed with this psak.

Rav Shafran concluded the psak with a note saying that who even knows if the prayer of notable rabbonim is more accepted than those of a young yeshiva bachur who is still protected and without sin...