Ibn Majah

(1)
Abdullah ibn Umar radi Allahu anhuma also refrained from narrating by mentioning the name of the Messenger of Allah sallallahu alayhi wa sallam for the same reason as the aforementioned other noble Companions radi Allahu anhum exercised caution—that is, they feared that, out of forgetfulness, they might attribute words to the Messenger of Allah sallallahu alayhi wa sallam which he had not actually spoken.

(2)
This does not mean that the Companions did not convey the religion; rather, the point is that their method was different. They would inform people that such-and-such act is obligatory, such-and-such is forbidden, such-and-such is permissible to do, and it is better to avoid such-and-such act.
These noble individuals would explain these rulings in the light of those hadiths which they had heard from the Messenger of Allah sallallahu alayhi wa sallam, but generally, they would not mention his name explicitly.