Symbolics' problem was not that their software was not portable. Open Genera is a VM and ran on DEC Alpha, it would have been possible to port it to other 64bit machines.
But the business went away. The thing was too costly. It was also not just a Lisp implementation, but a portable OS. As an OS it simply did too much: own networking, own window system, ...
The reason why Franz is still around and Symbolics' is not, is not a question of portability - it is because Franz' Lisp is just a Lisp implementation and concentrates on that - where Genera / Open Genera is an OS, which simply does too much. Why run a TCP stack in Lisp on a machine which already has a TCP stack? Why run a window system on a machine which already has one? Plus the rest of the machine does not benefit from that. If the other software could use the Lisp TCP stack, but it can't.
Franz started only a few years after Symbolics. I believe one of the key reasons they're still around is because their Lisp system is easily portable.
"Also, would the MIT Lisp Machine system or Genera have gotten as good as they did as fast as they did without outside funding (government and VC respectively)?"
Stallman was totally right about Symbolics though - they took all of their Lisp work and most of the Lisp community to their grave. There wasn't a lot preventing them from making their software more portable or open, but they made a business decision not to do that, which proved to be disastrous in the long term.
"Or look at the failure of GNU to produce a kernel."
That's because there's already other, better Free Software alternatives out there. Why work on HURD when you can work on Linux or one of the BSDs? And it's important to note that it's a continuing failure - because the project is Free Software, people can continue to work on it if they want.