Here's why:
* Lord of D's effect: Lord of D's effect only affects the summoning of Dragons. It does not affect the existing positions of dragons already on the field.
* Dragon Capture Jar's effect: Dragon Capture Jar's effect is a continuous trap that keeps dragons in the Monster Zone, even if they would normally be sent back to the hand or graveyard.
* Interaction: When Lord of D is summoned, its effect will not trigger the return of dragons to their original positions because Dragon Capture Jar's effect overrides that. The dragons will remain in the Monster Zone, even though Lord of D is on the field.
Therefore, summoning Lord of D will not make dragons revert to their original positions if Dragon Capture Jar is in play.