1) If I were doing due diligence on a vendor, and ran across something like this, I wouldn't buy from them. It's unlikely to come up (I've never done due diligence on a CEO), but if I learned a CEO had pulled a stunt like this, I wouldn't buy from a new company.
2) Actions like this bias my judgements to the entire buy vs. build decision, and the SaaS space. My experience is that each time a service provider pulls something like this, the cost is higher than any net benefit from having worked with that provider.
There are exceptions. There are vendors with long track-records of stability. I happily use AWS, and would happily use Azure. But I don't do business with Google because of a history of stunts like this (several affecting me), and I avoid small startups for anything business-critical for the same reason.
In finance, stability is especially key.
In the same way as firing employees impacts the morale of existing and potential employees, firing customers does the same.