I don't know based on the rulebook.

The rulebook on page 13 states that if there is a tie for most markers in a sector, the tie is broken in favor of the player whose marker was placed later. However, it does not address what happens if two players place their last markers simultaneously due to a card effect or special ability. There are no rules provided for simultaneous placement or how to resolve ties in that specific situation.

To answer this question, the rulebook would need to specify a procedure for resolving ties when marker placement is simultaneous.

Source: Core Rulebook (pp. 13, 18, 21, 28, 7)