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.
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.
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.
I have seen the "soft-hostile takeover" executed in other contexts, however. I don't think it's necessary to presume DHH used his influence as a Shopify board member to seal the deal or that he would have ulterior motive in doing so; in my experience, it's sufficient for a company to see a valuable piece of a puzzle they care about go vulnerable to acquisition offers to make the offer (with the corresponding stick). I'm willing to be convinced otherwise in either direction if more information presents itself; all I know is that Shopify put the offer on the table "We'll back-fill your funding gap or we'll make it much worse; your call." And I've seen that offer made in a completely capitalism-red-in-tooth-and-claw "business is business" way in the past.
You are alleging that Shopify was retaliating. Do you have any reliable context that Shopify was acting in a retaliatory manner?