Code:
<FreeUnit>UNITCLASS_SCIENTIST</FreeUnit>
<FreeUnitPrereqTech>TECH_WRITING</FreeUnitPrereqTech>
<FreeUnit>UNITCLASS_MERCHANT</FreeUnit>
No single row within a table can give data for the same column more than once. You have FreeUnit twice here, which causes the game to reject the entire contents of the file.
Even without the fatal syntax error there is a limit to how much stuff you can pile onto a single leader before the game will not add any more Trait Stuff to that leader regardless of whether the Trait Stuff is given all within a single Trait or is from assigning multiple Traits to the same leader.