Ohr ha'Chayim: This refutes any claim Bnei Ches might have had of Dina d'Bar Meitzra (when one sells land, the neighbors have first rights to buy). If Reuven buys from Shimon's Nochri neighbor, Shimon cannot contest it, for Reuven, says, I removed a lion from your border. This does not apply here!

Malbim: This was lest Bnei Ches protest that Efron transgressed the enactment (not to sell to a stranger a burial site), ¹ or Efron's family protest (that they retain burial rights in spite of his sale), All of Bnei Ches consented!

Ha'amek Davar: If not for this, there would be Avlah (injustice) in his burial there. A Mes does not want to buried amidst Avlah. This would override all the reasons why he wanted to be buried there!