Only five years ago, Kirk Cousins was a hot commodity in part because of his performance and in part because of an unusual circumstance.
He was a quarterback at a relatively prime age hitting the open market as a free agent. The marketplace in 2018 was such that quarterbacks like that were generally not available in trades or free agency. If a team had an above-average quarterback that it liked, the player was signed and off-limits.
What has transpired since then is reflective of a seemingly greater level of volatility in the QB marketplace, with high-profile passers changing teams frequently.