During the online poker boom there were many such stories. The amount of money moving around online poker in 2005-2009 was just insane.

Lots and lots of people went from 1k or less invested to moderately wealthy. I knew multiple people personally in college then who went from ~0 to > 100k.

Absolutely could have happened even if he played the lowest variance games available with good bankroll management.

All it would take is good streak (maybe luckbox some SnGs), move up the stakes, and have a good run in something like PLO to do the same in-a-day.

I played extensively and still have friends that play professionally, this type of story is not uncommon at all.

It happened to me and many people in my poker circle. If you played well, had good bankroll management, game selected and studied hard it wasn't nearly as hard as you think.

If the timeframe was right, around the middle to the end of the last decade, it was reasonably possible. I was the kinda guy handing them the money :-(