If your WordPress site is redirecting to spam, it has been hacked. Malicious code on the server or in the database is sending some of your visitors to a scam page, often only phone users and logged-out guests. The redirect is only the symptom. The backdoor that planted it will put it back unless you find that too.
The short answer
- A WordPress site redirecting to spam has been hacked; the redirect is a symptom of a backdoor, not a plugin setting.
- Cloaking hides it from logged-in and desktop users, so test with a mobile user agent via curl and a phone on cellular data.
- Check .htaccess or server config, home and siteurl in wp_options, theme JavaScript, the database, and plugins including mu-plugins.
- Remove the backdoor, regenerate salts, change every password, purge every cache, then request a Google Search Console review.