The 3 M's stopped this - Mattis, May and Merkel.
https://www.fort-russ.com/2018/04/germany-refuses-to-join-possible-us-intervention-in-syria/
https://thehill.com/policy/defense/382673-mattis-us-still-assessing-suspected-syria-chemical-weapons-attack
“Germany will not take part in the possible operation"
British Prime Minister Teresa May, during a telephone conversation with US President Donald Trump,
announced that London too needed more evidence of a suspected chemical attack in Syria to join the US operation.