YOU SAID:

he couldnt fit the coat in the bag because it was to big

INTO JAPANESE

大きすぎたのでコートをバッグに入れることができませんでした

BACK INTO ENGLISH

I couldn't put the coat in the bag because it was too big

INTO JAPANESE

大きすぎてコートがバッグに入れられませんでした

BACK INTO ENGLISH

The coat was too big to fit in the bag

INTO JAPANESE

コートが大きすぎてバッグに収まりませんでした

BACK INTO ENGLISH

The coat was too big to fit in the bag