As I once heard directly from R’ Brevda (who should be zoche to a refua sheleyma) after the World Trade Center attack.
“Davening is a vadai mitzva,
Krias Shema is a mitzvas d’oraisa,
Talmud Torah – Kinegged Kulam
Understanding why Hakadosh Boruch Hu decided to do what he did in the USA, Sofek.
Ein Sofek Motzei Middei Vadai”