In Eldritch Horror, when a monster causes the closest investigator to move one space closer to the monster, but more than one investigator is on the closest space, who moves?
The final decision is always down to the active investigator when you are deciding the nearest but two or more targets are an equivalent distance.
From the rules reference (page 9):
When determining the “nearest” space or token, find the space or token separated by the fewest number of interconnected paths.
- If two or more spaces are tied for nearest, the active investigator chooses