Why didn't Yosef's brothers bury him where he asked?

Question

So Joseph made the Israelites swear, saying, “When God comes to you, you shall carry up my bones from here.”

(Bereishis 50:25)

And Joseph died, being one hundred ten years old; he was embalmed and placed in a coffin in Egypt.

(Bereishis 50:26)

We learn that Joseph's bones were later brought out of Egypt by Moshe Rabeinu (according to Shemos) and/or the B'nei Yisroel (according to Yehoshua), resulting in the fulfillment of the covenant. But why didn't Joseph's brothers themselves bring his bones out of Egypt, according to his last wishes and their own promise? Are all of Joseph's brothers guilty of a significant aveiro through their failure to do this?

Answer 1

The OP quotes a verse that has Yoseph saying: "When G-d comes to you..."

Yosef planned on being buried in Egypt. He simply wanted to leave when everyone else did. By that time, his brothers had already passed away and were themselves taken out of Egypt by the B'nei Yisroel.

Answer 2

As I explain in Vayigash - Why didn't the family go back?, Par'o only allowed Yosef to bury Yaakov in Eretz Yisrael because of the oath Yaakov had made him swear. Even then, he forced the brothers to leave the families behind as hostages. Once Yosef died, the brothers could no longer leave Mitzraim. Thus, they were unable to even take Yosef out for burial.

Additionally, Yosef made them swear that he would be taken out when the entire Bnai Yisrael left Egypt. That was something that could not be done until Hashem took them out and supported them in the midbar. Had they tried to leave on their own (even just to take Yosef for burial), they would have wound up like the band from Efraim that made up the valley of the dry bones.