Trust. You talk about trusting the Federation. You throw it around like a leaf in the wind, but you don't remember. If memory serves, after the Earth had its own Burn and Cochrane made his historic warp flight that was detected by a Vulcan survey ship, the Vulcans made first contact with humanity. The Vulcan's reached their hand out, in good faith and took the Earth under its wing. From that point on the Earth changed forever. Fleets of starships were built that gallantly explored the galaxy and spread the core values of the Federation to planets that were fledglings and might not have survived. You talk of trust and that Nivara was the reason for the Burn and that the Federation might, exploit the data within SB-19 for its own purposes. But what about the purposes of the Vulcans in making first contact with Earth? Was that an exploit? Because of the Vulcans interfering in the progress of the Earth of its first successful warp flight, hundreds of billions of lifeforms across the galaxy died in the wars that resulted due to that first successful warp flight and the Vulcans, being ever the deep and curious species the Vulcans are, coming looking. But that is neither here nor there and the past is already gone. In another Burn that the Federation is now returning the favor, reaching its hand out to the Vulcans...and Romulans in a first forming of the Federation where the Federation is now that survey ship and Nivara is Earth. I am certain that Vulcans are eager to put their science ships back to work just as I am certain that the Romulans are keen on finding their old ways put to use, once again for both Nivara and the Federation. When there's a Romulan in the delegation, one must be always be the Warbird that de-cloaks right in front of her. Romulans never change. No matter 2250 or a 1,000 years in the future, there is one thing that will always remain a constant. Vulcans and Romulans are still warm, sociable and green blooded as ever. Simple logic. Some Tennessee Whiskey? It might take that pointiness out or those attitudes of yours. -Dr. Leonard McCoy, Chief Medical Officer, U.S.S. Enterprise.
Why? It's not a spoiler. As a Doctor you have to remember how to smack both the Romulans and Vulcans on their behinds to get them to take first breath after being born.
I find it ironic that the Romulans of all species would want to stay in the Federation and not the guys who actually FORMED that damn thing. doesn't that seem suspicious? anyone?
Not really. The Vulcans always had a massive chip on their shoulder even after the Syrranite reformation. They were generally dismissive of other races and could be at times down right racist. Also, there were Vulcan isolationist movements even in the 24th century. It doesn't surprise me one bit that the Vulcans would secede if they felt staying in the Federation was no longer the logical choice.
Also, I'm going to assume that whatever attempt the Romulans made of forming a new government after the Star Empire fell probably didn't last. We see glimpses of this in Picard where former RSE territory is now split into many different factions competing with each other. By the 32nd century the Romulans probably wanted to maintain the security and stability that being part of the Federation offered, even post-Burn (or perhaps especially post-Burn) then leave the Federation and risk a repeat of what happened for them after 2387. The Vulcans meanwhile were under the impression that they caused the Burn as a result of pressure from the Federation government who had ignored their cautions that something catastrophic could happen. To them the matter of leaving the Federation was considered strictly logical.
Not really, no. The Vulcans have always demonstrated a tendency to be very insular and keeping information, even from allies. If the Vulcans see no benefit in the Federation then they wouldn't stay.
From Enterprise to even TOS, it seemed Vulcans always had a slightly uneasy place in the Federation. T'Pau turned down a seat on the Federation Council, the only one to do so. Vulcans in Enterprise were isolationist and it was really only gratitude after Archer saved Surak's katra that they decided to start doing what he said (including presumably joining the Fed). There didn't even seem to be much of a Starfleet presence on Vulcan in Star Trek 4, for example, to escort Kirk back to Earth for trial. The Romulans got their isolationist tendencies out of their system a long time ago. The silence between the Romulan War and Balance of Terror, and their silence between the Tomed Incident and TNG. They built an entire empire where it was "Romulans first". What did that get them? The destruction of their homeworld, and the deaths of most of the Romulan race due to their own religious extremists, the Zhat Vash, destroying their evacuation fleet. If the Romulans had been with the Fed from the start, the Zhat Vash would never have risen in power to even remotely be able to sabotage a Romulan evacuation. The Romulans already know what isolationism got them. They don't want to go back to that. The Vulcans are still dreaming of the "good old days" where they did what they wanted until they unintentionally became indebted to Jonathan Archer. It makes complete sense that most of the Romulans would want to stay in the Fed and the Vulcans would want to leave, if you think about it.