To do that, St. Paul would need to make all the other 12 apostles buy into the story and start spreading it. Then do the same with the extended 70 apostles and their disciples. And, of course, change the gospels.

In addition, the "concept of Jesus" is something that's woven throughout the Old Testament. St. Paul would have to go back in time and change the Torah and books of prophets like Daniel and Isaiah.

It's interesting that every point of this narrative conflicts with the canonical accounts (even excluding the Pauline corpus for this purpose), in which Paul did encounter Jesus, and did at least spend time with (we aren't explicitly told it was spent in study, but presumably it was not exclusively in silent meditation) with disciples of Jesus between the encounter and conversion experience and the start of his ministry, and he got along as well with the other apostles as the other apostles they did with each other.