I think there’s a misconception that he just walked into a random pool hall one day and ran 526 balls on a random table. He was hired by Brunswick to promote their products, these tables were prepped ahead of time for him. Good playing conditions were part of the show. He was doing multiple exhibitions in a day, doing over a hundred exhibitions in a year. He was constantly playing and making high run attempts.
Mosconi also stated that he ran over 600 in practice. Sigel and Varner also chased the record in practice. So the idea that modern players are uniquely taking endless attempts in a vacuum doesn’t really hold any water.
You are wrong on several counts.
The tables were not "prepped for him -- he probably got new cloth, that's it.
And, he was not constantly making high run attempts -- he was playing a local to 125. He'd often play a low percentage shot like the front ball into the side, or a corner ball one rail bank to give his opponent a running start. Then, when it was his shot, he'd often turn to the crowd and ask them if they'd like to see a 100 ball run.
Then he'd do it.
He was doing that on a different tables, and in different rooms, somewhere around 300 times a year all around the country. Other than running 100 or making it to 125 there was no high run attempt. At the conclusion of the match he'd shoot a number of trick shots, hang around, sign some autographs and call it a night or be off to the next town and do it again. I know this because I witnessed it several times growing up in San Franciso where he'd come to do an exhibition every year.
Lastly, he was not chasing his own record. The only reason he ran the 526 in Springfield, OH was that the room owner was some kind of friend and Mosconi said he wanted to put on a good show for him. So he played his match that night to 200 points v the usual 100/125. His opponent ran three. And when Mosconi got to 200 someone in the crowd urged him to keep going to see how many he could get. IOWs, his attempt that night was a one-off.
He ran the 600 while warming up in his hotel run before one of his matches with Fats. Charlie Ursetti was racking for him and at one point they broke for lunch. Then Mosconi kept running balls, put down his cue, the run unfinished. He didn't chase or care about it.
Lou Figueroa