The New York Times asks. The crux of their answer:

“Ms. Stefanik’s story is important in part because it mirrors that of so many other Republicans. They, like Ms. Stefanik, are opportunists, living completely in the moment, shifting their personas to advance their immediate political self-interests. A commitment to ethical conduct, a devotion to the common good and fidelity to truth appear to have no intrinsic worth to them. These qualities are mere instrumentalities, used when helpful but discarded when inconvenient.”