Consequently, I have assumed that the following happened. The FBI already had information that Page was something of an apologist for the Putin regime — although the record, we shall see, is more complex than that. Thus, the FBI and DOJ may have combined that information with some claims mined out of the dossier; but they would not have included Steele’s claims without corroborating them independently. This combination of information, doubtless added to by intelligence not known to us, was crafted into the application presented to the FISA court. This would be the normal, appropriate process.
Exactly when during the summer of 2016 the surveillance of Page began is unclear. Importantly, however, an unidentified government official told the New York Times that the FBI and DOJ waited until Page was no longer part of the Trump campaign before seeking the warrant — investigators being leery of crossing the line of direct spying on a political campaign member. The Trump team distanced itself from Page in early August, so it was presumably around this time when monitoring began.
To summarize, it is entirely possible that a surveillance warrant for Page was obtained based on no information from Steele, or at least no information the FBI had failed to corroborate independently.