You say exploded from nowhere, but wasn’t Froome riding for years on crappy teams/equipment busy getting noticed, then really started taking off when he moved to a proper pro setup? (Though even then it took him several years to ramp up to TdF-winning form)
Much is reliant on the biological passport, so anyone who has mysterious upticks mid-career should create red flags. I’d be more worried about newcomers who set the passport at a high level.
That said, Jumbo-Visma have already been called out on Ketone use, so I guess we’ll see in time if that’s proven/ruled to be performance-enhancing.