Why specifically an Eglah Arufah?
Possibly Yaakov felt that he was at fault for what happened with Yosef. Yosef is saying – as long as you did your due diligence (walked me 4 amos, physically and metaphorically by preparing me for life), there is no fault.
explanation of Eglah Arufah itself – why the closest city and specifically elders? if he unexpectedly died on the road, he might have been infected in the last city he stayed in. Elders are saying that they maintained proper public hygiene., social distancing and masking. If they would even taught that person a lot of Torah while coughing at him, they would still be guilty.