Pine originally left because they went against what he signed his contract for when they said they were going to pay him less.
It's greed.
And yeah, you're right. There's risk. Like my house getting hit by an asteroid. Or my neighbour getting struck by lightning through an open window on a sunny day. Everything has risk. Thank you for reminding me.
But Star Trek 4 released at a decent time after Beyond? Sorry, there's minimal risk. Money is there. They just wanted Marvel money. Anybody that followed any news article from the time is more than aware of this. 1 million percent greed.
To quote Chris Pine (I'll take his word over yours, amongst, as I said, EVERY other person commenting on the situation at the time):
"We always tried to get the huge international market. It was always about making the billion dollars. It was always this billion-dollar mark because Marvel was making a billion. Billion, billion, billion."
Greed.