Protectionism is a valid reason to deny it

No it isn’t. Protectionism is jingoist bullshit. Always has been, always will be.

I wonder if denying Chinese tech under the guise of national security a last ditch attempt from big oil lobbyists?

Definitely. The leadership of both major US parties are pretty much owned by the fossil fuel industries.

Even progressives advocating for the Green New Deal won’t say the part about gradually eliminating fossil fuel use out loud out of fear of fossil fuel industry lobbyists and the politicians they own doing an AIPAC.

Or is that too far fetched

Not at all.