For some reason we are not educated about this. We learn it the hard way by being taken in with what seems a good opportunity, then getting abused and then going our own way. We naively believe people empathise for others in the mistaken idea that there is some semblance of 'compassion' in everyone.
Even if we have gone through the mill several times we may not be educated as to what is only going on. You have to be done over by someone at the extreme end of the spectrum of personality disorder to understand what really goes on with the tyrants and bullies that frequently own companies, start-up or otherwise. We even elect these 'personality disorder' types to high office without anyone pointing out that they are not fit for the role due to having these psychopath tendencies.
This really does have to be a regulatory issue as those that cannot think through the consequences of their actions or empathise with others or understand the harm they do need to be rendered powerless. Otherwise they will not learn their lesson and go on to waste yet more lives. They can do so near indefinitely, taking people on a ride for six months or more before their victims cotton on to what is happening.
There is a second problem in that the people with these personality disorders really do attract others. Cult leaders do it, to attract others with personality problems of their own, elsewhere on the spectrum. For instance, in this case, marketing. What type of person does marketing in the first place? What leads them to believe they have the secret sauce to market the product they know nothing about? There is some self-belief going on there, some belief that isn't grounded in a strong product that the customer-base will 'market' using word-of-mouth. Sure there may be some good experience and education that can be brought to the problem but often there is not.
It is important to learn the 'tells' - as other commentators have noted it is how people treat restaurant staff that says it all with these rogues. Also the 'there is no I in team' really does matter - do they say 'we' or 'I'? Sometimes we overlook these 'tells' for reasons we invent - maybe they have were brought up that way... We give them excuses for their behaviour. We keep our anger at them to ourselves and don't burn our own bridges by letting that anger out.
It is a pity that most people only get 'lightly burned' in these situations and not fully toasted. Only when you get fully toasted can you work it out properly and end up knowing about the rogue personality types and how toxic they are.
obviously, there are personality traits and disorders which predispose a person to doing bad things. But that isn't a reason to assume that's what happened here, unless you happen to be that person's licensed psychiatrist.
It doesn't take a mental disorder to be shitty.