I mean, it's alleged they were a phishing operation...

And in terms of trademark law the owners are unlikely to be on stronger grounds if they're not a pure phishing operation as alleged, but have merely chosen to include Facebook's trademark in their website or email marketing name without Facebook's permission to increase the likelihood Facebook's customers will purchase services from them.

You don't have to imply you definitely are the owner of a trademark to fall foul of trademark law, you just have to be trying to profit from using the trademark without permission in their line of trade in a way you can't justify as 'fair use'. I think we can rule out the idea instagrambusinesshelp.com is commentary, comparison, parody or a list of third parties worked with.

But you have to consider your everyday user who has no real understanding of how companies use domains outside of being a name. That domain suggests it's business support for Instagram.

I feel like an everyday person would see that and think “ah a 3rd party consultant to help with my influencer business” (or whatever the professional application of instagram is.)