And my boss knows that, and it's okay for executives to make corporate decisions for personal reasons. It's not okay for executives to make corporate decisions for personal reasons without acknowledgement, and particularly not with explicit deception. The difference between "my product is better for intangible reasons" and "my product is better because of lies out of teeth is fraud.

Taking personal kickbacks from vendors can be legal, so long as it's reported to your employer (and the IRS). What's not legal is hiding it from your employer because they have policies against it, and every (large) employer does.

The sole owners of large private companies can and do occasionally get personal kickbacks for their business. It rarely makes sense for them, because as owners of large private corporations they have better way of extracting cash from those companies (like literally paying themselves a salary or bonus). Totally legal, though.