If there's a reason to leave, it's that the situation might be too far gone to salvage. From the one side we can see here it seems unlikely that the CTO has kep

If there's a reason to leave, it's that the situation might be too far gone to salvage. From the one side we can see here it seems unlikely that the CTO has kept this conversation/complaint limited to the OP, and his desire to remove one of the founders is already undermining that founder's leadership position in the company. Getting out with compensation for the equity or accelerated vesting might be the best case scenario, depending on how far this has gone.