Someone on Youtube wrote in a comments section of a video about founders of religions relying on converts not being able to verify the founder's religious experience. For example, if someone has no witnesses to confirm that he has been visited by angels (whether he was lying or imagining it), someone gullible enough might still take his word for it. Or, he might claim that the miracle happened/would happen long enough in the past/future that it was impossible to verify.
He said that people apply to Christianity this rule about how religions get off the ground through gullibility. They assign later dates to the gospels because in order to get people to believe the accounts of miracles, they must have been recorded a long time afterwards when there was no way of verifying them. Since this is the only way to get people to believe in the miraculous (apart from having no other witnesses and relying again on gullibility to convince contemporary converts), the stories in the gospels must have been made up long enough after they were supposed to have happened for verification by witnesses to be impossible.
However, there is strong evidence the stories were written down pre-AD70. A five-sided pool in Jerusalem, mentioned by John as still in existence, was destroyed by the Romans. There is no mention of the deaths of James, Peter and Paul in Acts, which we know to have happened before 70. Luke would almost certainly have mentioned this, and the persecution under Nero, had he written after those events.
If as this and other evidence suggests, the gospels were published before 70, then the genealogies must be reliable. They would have been checked against the records, which were still extant in Jerusalem.
So we are then at liberty to make inferences as to why they differ in places.