What you believe and what you can document are two separate things.
Per the concept of "innocent until proven guilty", there is no burden on Shopify to prove they didn't do what you believe. The burden is on you to provide evidence for the motivations behind their actions.
I personally doubt Tobi got Shopify to where it was by making rash decisions based on emotions and drama.
Not only does one have to do the right thing, one has to be seen doing the right thing, because actual malfeasance and the appearance of malfeasance are indistinguishable on the outside. Though I wouldn't be surprised if Tobi/Shopify doesn't care for what the little people think, so this rule-of-thumb may not apply.
Your second para is appeal to authority. A former CEO of mine (not a billionaire though, but a mere centimillionaire) was a drama magnet, thin-skinned, and a vengeful little shit.
Given the power dynamics, the burden of proof is on Shopify to proove it wasn't retaliating at the behest of, or in a misguided attempt to defend DHH's honor.