The fumbles are definitely a larger issue, but there was also more of those last year in the first 8.5 games.
Of the QBs who throw 550+ times in a season, I’m willing to bet none of them run even half as much as Allen, and none have even a fraction of the ground production.
When you throw more than most, and run more than most, you’re going to have more opportunities for turn overs.
More opportunities for scoring too, he’s always in the top 3.