Or maybe they wanted to spend their energy actually solving their problems rather than trying to persuade the maintainers of other projects about their approach. For example, could they have proposed some changes to IPVS to get rid of multicast for state sharing? Maybe. But then they'd spend all that time arguing with other users of that project about the relative merits of each. Instead they built a new solution and users now can have a choice, including the choice to take some of these ideas and apply them to the other projects if they are clearly superior.
I would accuse them of NIH if they simply reinvented another wheel when there was a perfectly acceptable solution already out there. But it doesn't seem like that was the case. Instead they clearly evaluated the existing solutions, found shortcomings, and decided to solve those problems for themselves, and then publish the resulting code. I see nothing wrong with that approach.
