In spring and early summer when the hormone testosterone kicks in, some local wild roosters get a little "macho". I would suspect that this crazy pheasant was born nearby.
I would say that a wild pheasant chasing a riding lawnmower is not normal. But we have to remember that some wild pheasant don't perceive moving machines as predators. A farmer friend tells me that sometimes when riding a tractor pheasant sometimes stay close.
I remember years ago landing in a commercial plane in Goodland, Kansas (in early May) seeing wild pheasants in field along the runway. Taking off seeing wild pheasants 15 to 20 feet from the runway in the grass, and the loud jet engine did not scare them.
I would guess that these wild pheasants hatch close by in the field near the Goodland airport and heard the sound of planes since they were chicks.