doesn't look like anything untoward here. the league has injuries turned off so you can leave a cheap mop-up in to get slaughtered when the game gets out of hand. your opponent seems to have started the game with a real lineup, but then when down 8-1 in the 7th the mop-up came on and took a beating to rest everyone else.
also fatigue for position players gets capped for single games, the most PAs a hitter can be credited with in a game for fatigue purposes is six, to prevent someone doing this on purpose. but I don't think this owner did anything sketchy or deliberate in this case.