Possibly Merriwell, wishing to encourage Blunt, gave him the initial advantage.

A minute, or a minute and a half of fierce, silent struggling followed, Blunt blowing like a grampus and Merriwell taking it easily.
With an arm clasped around Merriwell's neck, Blunt labored tremendously to turn him over.

Merry, however, was like a rock, and all the cowboy's efforts failed.

He expended a vast amount of strength, which was exactly what Merry wanted.
Then, with startling suddenness, Merriwell from a rocklike, passive defense became the aggressor.

He seemed to yield to Blunt's pushing and hauling, but that supposed yielding was a sorry disappointment to the cowboy.