This is not how I remember how and why Starfleet ended up at Bajor. There were lots of reasons why the Cardassians abandoned Bajor, and I think a major one was moreso that Bajor was becoming a subject planet of diminishing returns; the resistance was out of hand and the occupation's grasp was waning, combined with the low moral of losing so many soliders to a 'primitive' planet, as well as the natural resources being not as plentiful after 50 years of occupation where the Federation did nothing. As far as we know, the occupation began before the Federation had real dealings with the Cardassians. The war between the Federation and the Cardassians appear to have been border skirmishes and not a crusade against Bajoran slavery. It was only after the Cardassians left that the Bajorans requested the aid of the Federation, which is perfectly okay with them; Bajor was not prewarp and directly requested aid; the Prime Directive does not apply. Bajorans as a subject species of the Cardassian Empire and the unrest of being so is an internal affair of the Cardassian Empire, and thus the Prime Directive did apply.
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IDK if I'd characterize it as 'political pressure from the Federation' per se as it was part of the Federation/Cardassian p[eace treaty of teh Feds own direct war with the Cardassians (and in all the years of TNG and Ds9, while the end of said war was chronicled; the reason for the start of it never was n- and supposedly, it went on as far back as Picard's command of the Stargazer, through the first 3 Seasons of TNG - even though that fact was NEVER mentioned until TNG's 4th season.
But my point? The Bajor System and DS9 were ceded to the Federation in the same way A LOT of former Federation territory (with established Federation Colonies that the Feds TRIED like hell to get their citizens to move or move from) was ceded to the Cardassians. (And that left A LOT of disgruntled former Fed citizens to form the Maquis).
So again, I don;'t think you can say the Federation exerted any more 'political pressure' then the Cardassians did towards the Federation to get the Territorial concessions it received as part of the treaty.
^^^
The treaty itself was to end a direct war between the Federation and the Cardassian Empire. The Federation didn't appear to be lobbying for or against getting the Bajor system itself no longer being classified as being in Cardassian territory per se - it was part of a vast amount of territory that changed hands on BOTH SIDES.
Yes, the Bajorians IMMEDIATELY applied for Federation membership once their star system was no longer classed as being in Cardassian space; but again, I don't see any evidence that the Federation specifically cared if Bajor was included or not.
Bajor was invaded by Cardassia 60 years (and that's in on screen dialogue) prior to the start of the DS9 series. Unless the Federation/Cardassian war started and ran that long, I seriously doubt the plight of the Bajorians weighed very heavily on the minds of Federation diplomats from that time, until the time the Federation/Cardassian War started,
To be quite honest: It's a long time ago.
But even Memory-Alpha says political pressure from the Federation was at least one of the reasons for the Cardassians leaving Bajor:
https://memory-alpha.fandom.com/wiki/Occupation_of_Bajor
And I remember something similar from Picard somewhere (probably a Ro Laren episode), where he specifically talks about political pressure.
Now I fully aknowledge this: This was most likely not the
only reason. All of that was way
after the Federation-Cardassian war. And that Cardassia hasn't occupied other planets since then. And that it was Cardassias
civil gouvernement that decided to stop the occupation, not the military leadership. So it was probably a number of reasons, diminishing returns and a change in leadership included.
But one thing is pretty clear: The Federations
did put political pressure on to end the occupation! Even if it wasn't the ultimate reason for the success - they tried. the Prime directive didn't apply here, all of this was really "Realpolitik" (which DS9 was really good at) - wanting to help make the situation better, but at the same time not increase tensions with the Cardis too much.
That's why it's su curious tha Ba'Ul / Kelpian - relationship is under the "prime directive". I don't know why at this point, maybe even the writers haven't figured the situation completely out at shis point - but it looks to be an interesting, slightly more complex situation, and I#m always looking forward to such.