First off, I don't believe one needs any "official credentials" to coach. I don't have any.
Although I do have 25+ years of running experience on pretty much any surface any distance (I've had the good fortune of running lots of different races from NCAA D1 track 800m-10km, xc, to half a dozen sub 2:20 marathons and tons of ultra-trail-mountain races).
Personally, I am less comfortable coaching someone for a 100-mile ultra race compared to a marathon though...because personally I have not done very well 100-mile races (compared to shorter distance races). Still we sell training plans at Higher Running for lots of ultramarathon racing (my partner Sandi has developed good 100-miler workouts and protocols as she has done well at those kinds of races!).
But yes there does seem to be this rise in "influencer coaching and tips" from runners that just started running a few years ago and have run a couple marathons. I guess sometimes people need "more of a cheerleader instead of a coach" and that "bro-science" often trumps actual science.
As someone who has also been doing running Youtube videos for over 15 years I've seen the same cycles of videos and content over and over. Quick, clickbait fixes and slick editing. "Subjective shoe reviews" by people that barely run in the shoe, might have a weird footshape and form and have never worked in speciality running or seem to not know anything about materials and biomechanics. Short form content on TikTok and IG reels have also changed the game imo. I actually like some of it, although I shoot with an old iPhone, an old GoPro and a very old Sony.... in 1080.
People with money generally win the "influencer game" because once you can devote a lot of time and resources to content creation (or pay others to help push it for you!) it's a matter of getting more paid gigs, more clicks, more Google Ad money, and selling things like merch. Travel and racing frequently and getting free gear and shoes is not a problem. Training time and filming time and getting new camera equipment is not a problem (perhaps it never was though if you came from money or had a lot of it beforehand). It certainly takes a certain personality and degree of narcissism (which I admit I have).
Anyway fun fact: I first met my friend Stephen Gnoza as well as Ben Parkes and Sarah all at the same running camp several years ago.