Why were the French placed between the British and Russians?

Why did the Allies sandwich the French squadron between the British and Russian columns?

They were not confident in the French admiral and wanted stronger commanders on either side.

Coalition formations can encode command relationships as much as tactical geometry. The French column followed the British and was kept immediately ahead of the Russians. That placement bracketed Rigny's squadron between Codrington and Van Heyden, the two commanders with greater naval experience. The answer ties the arrangement directly to their doubts about Rigny's judgment and ability to handle a large fleet action.