OK in case this helps anyone it could be some weird issue with running VMWare ESXi within KVM. Keep in mind we enabled nested KVM so technically it should work.
I am not sure why the whole network went down on the ESXi host when the vCenter appliance would startup still. We also tried changing the NIC model in KVM we tried everything: virtio,e1000,rtl869 etc..with the same result.
We used the exact same .json config file and threw it at some of our baremetal servers and everything worked fine (aside from the fact that if you have strange characters like * or ) in the password then it will cause the appliance install to fail. It looks like there may be some compatibility issues between KVM and VMWare or a bug in either sides code (I am moreso thinking KVM as the nested part is still said to be experimental).
Hope the above helps someone.
Cheers