Benjamin Sisko is prone to emotional outbursts. He has a foul temper and has poor emotional control compared to Picard. Why was he put in command of DS9 given these weaknesses?
Bosses with foul tempers make poor leaders because they are unpleasant to work with. Would you want to work under such a boss?
Following the death of his wife during the battle of Wolf 359, Sisko was on the verge of leaving Starfleet. We clearly see the trauma he was grappling with during his interactions with Picard. Before he resigned his commission, however, he was nominated for the commanding position at Deep Space Nine by Vice-Admiral Leyton.
Leyton was Sisko's former commanding officer, the two having served together onboard the USS Okinawa. It's worth noting that Sisko was originally an engineer, and only joined the command division after Leyton recognized his potential and promoted him to executive officer. Leyton also ended up being an antagonist later in the series when he tried to initiate a coup against the Federation.
Sisko certainly didn't want the assignment at DS9; he said in the pilot episode that he was still considering leaving for civilian service on Earth. But I think he very quickly got irrevocably caught up in the situation when he was named the Emissary of the Prophets--a position which made him uniquely well-suited for facilitating the Bajoran entry into the Federation.
Therefore, we can infer that he given the assignment because Leyton was pushy and kept it because of his ties to the Bajoran religion.
Out of universe, I'd say his propensity for emotional outbursts was a deliberate attempt to distinguish the character from Picard and to emphasize the literal and figurative distance between DS9 and the Federation proper. As I recall, his attitude was more help than hindrance on many occasions!
Before he could resign his commision, however, he was nominated for the commanding position at Deep Space Nine by Vice-Admiral Leyton There were several years between Wolf 359 and him getting the transfer as I recall, that's plenty of time to quit; Data, Troi and Dr. Crusher have all resigned effective immediately before (Measure of a Man / The Loss / Sub Rosa)
Commented
Dec 16, 2016 at 11:17
As the previous answer states, Benjamin Sisko was given the command of Deep Space 9 while having the rank of Commander.
At the beginning of his career, he was more interested in engineering than in command. It was then-Captain Leyton of USS Okinawa that promoted him to the rank of Lt. Commander and position of Executive Officer.
LEYTON: Ironic, isn't it? When you came on board the Okinawa, you were more interested in engineering and ship design than command. But I promoted you to lieutenant commander, gave you the post of executive officer, and taught you everything I knew about being a leader.
Which would mean that Capt. Leyton was satisfied with Sisko in the command division and saw potential in him.
Later on, Benjamin Sisko was given the position of XO on USS Saratoga. Which would once again suggest, that he was still a good material for a Captain, or the position of commander of a station/ship.
After the events of Battle of Wolf 359, Benjamin Sisko was given an assignment at Utopia Planitia shipyards.
PICARD: [...] I have been made aware by Starfleet of your objections to this assignment. I would have thought that after three years spent at the Utopia Planitia yards, that you would be ready for a change. DS9: Emissary
We can see that at least Capt. Picard thought that a change in position would be suitable for Sisko, even if it was only his personal opinion (it might not be included in the decision process).
LEYTON: Captain Sisko. This is my adjutant, Commander Benteen. Benjamin was my executive officer aboard the Okinawa. And a damn fine one too.
SISKO: I did all right.
BENTEEN: Ah, don't be modest. Admiral Leyton has had his share of executive officers and you're the only one he ever speaks fondly of.
LEYTON: Present company excluded.
SISKO: Admiral Leyton is the one who recommended me for the job on Deep Space Nine.
LEYTON: One of my better ideas. You must be Odo.
I think we can reach the conclusion that since Sisko and Leyton served together on USS Okinawa, until DS9: Paradise Lost (or maybe even further in a way), Benjamin Sisko was highly regarded as an officer and commander of Deep Space 9 by Captain/Admiral Leyton and it is stated clearly that his recommendation was a major factor in choosing the commander of the station.
Remember that at the time when he was appointed, DS9 was in no way a place of any importance.
Here is what Major Kira says in DS season 1 Emissary (ep 1):
KIRA: I don't believe the Federation has any business being here.
SISKO: The provisional government disagrees with you.
KIRA: The provisional government and I don't agree on a lot of things which is probably why they've sent me to this god-forsaken place. I have been fighting for Bajoran independence since I was old enough to pick up a phaser. We finally drive the Cardassians out and what do our new leaders do? They call up the Federation and invite them right in.
So actually, commander of DS9 is a backwater post. It would be a good place to recover from the emotional trauma with all the work that needs to be done to repair DS9 and make it operational without endangering any significant Starfleet missions.
He was in command after Wolf 359 because he had good connections in the top tiers of government (like Curzon Dax) and don't forget that Admiral Layton personally recommended Sisko for the assignment.
He wasn't captain when he was appointed to run DS9. By the time the wormhole is discovered he is too much involved in the Bajoran culture to just replace him.
After time passes he is promoted for his accomplishments despite him being a hothead.
