[leanstartupnoob]

Seems like you are the one being uncharitable.

For better or worse there are tons of both reasonable and unreasonable factors as to why a large company would replace a part time developer's side project with something that costs 9 figures.

You don't know those reasons, the person you replied to doesn't know those reasons, and in fact the OP probably doesn't even know those reasons (they "used to turn up to that customer annually for maintenance").