>His study of more than a billion hands of online Texas Hold’em found that 85.2 percent of the hands were decided without a show of cards. In other words, players’ betting decisions were of overwhelming importance in determining the outcome.

It is worth noting that the other 14.8% of hands, where a showdown is reached, are typically the ones where (much) larger amounts of money are exchanged.

So, betting decisions might decide the outcome of a majority of hands, but it's unlikely this corresponds to a majority of the money flow.