A cadre of powerful former cops at City Hall — including Mayor Adams and Deputy Mayor Phillip Banks — and warring NYPD factions pushed Commish Keechant Sewell to her “breaking point,” The Post has learned.

Adams allowed a power struggle and breakdown of chain of command to foment in the NYPD, leaving Sewell powerless at times to run a police department where longstanding feuds and loyalties to opposing parties are currency, according to sources.

“Everyone has a breaking point,” a source said, referring to Sewell, who finally abruptly up and quit Monday, blindsiding the mayor. “I don’t think it was one thing.”

Another source, noting the reputed lack of support that Sewell faced, said, “How does anyone navigate that?”

Sewell, as an outsider pick to run the country’s largest police force, was always going to face strong headwinds to make any changes in the NYPD, with practices and policies long ingrained in the culture, sources said.

But Adams, a former cop, virtually tied her hands from the start by creating a culture in his administration that allowed NYPD chiefs to bypass their commissioner by either reporting directly to Banks, deputy mayor of public safety who less than a decade ago served as the chief of the department, or going to current Adams aide and ex-cop Tim Pearson.

“The NYPD created the mayor, the mayor took all his friends with him, and she was not among the chosen,” a source with knowledge said. “It’s hard for an outsider if you’re not from that culture to fit in.”

NYPD commissioners have historically selected their leadership team, but Adams’ transition team, which included Banks and Pearson, had already filled the second spot in the NYPD, first deputy commissioner, with Edward Caban even before Sewell had the job.

Sources have said Adams and Caban are close.

During the first few months of 2022, Banks, who was only a few years removed from the department and still had close ties to a number of cops high up in the ranks, repeatedly went around the commissioner and called three-star chiefs into meetings to influence a series of moves.

Banks even personally fired the head of Internal Affairs Joseph Reznick, who led the internal probe into Banks during the NYPD’s corruption scandal, in which the former chief was named an unindicted co-conspirator, according to sources.

Banks abruptly retired in 2014, and it was later reported that his exit came as the feds were looking into hundreds of thousands” of dollars in Banks’ bank accounts. He has not been charged with any crime.

Sewell eventually brought in two confidantes from her time in Nassau County to help her at the department — but Banks and Pearson continued to work behind the scenes.

“[Banks] still knows a lot of people in the agency that he turns to get things done — that does complicate things for any police commissioner,” former Chief of Department Ken Corey told 1010 Wins on Tuesday without elaborating.

Sewell also was undermined in July when NYPD Chief of Training Juanita Holmes did an end-run around the commish to get the mayor to approve removing the time limit on the 1.5-mile run for new recruits at the Police Academy, sources said.

Sewell and Corey had quashed the idea of easing up on the physical requirement — but Holmes got the mayor to sign off on it by going outside of the chain of command and directly to him, sources said.

Holmes, a longtime friend of Adams and once a candidate for commissioner, also went around Sewell the next year with the unapproved appearance of Cardi B at a Girls Talk event at the Police Academy in Queens.

Sewell was furious she hadn’t been consulted about the event beforehand and upset the raunchy rapper was chosen to talk to young girls, sources said at the time.

But the mayor later specifically hailed Holmes as “brilliant” for the event.

Meanwhile, NYPD Chief Jeff Maddrey, a friend of Adams, formed his own internal department faction after he was named Chief of Department in November once Corey retired, according to sources.

Maddrey was not Sewell’s pick for the job, sources said.

The chief then oversaw a massive shake-up in the ranks, and he named a number of chiefs to top spots, including Chief John Chell, who the police commissioner did not want for the role, according to sources.

“All the leadership is not her pick,” according to a source with knowledge of the shake-up.

In the months that followed, Banks seem to lose some power as Maddrey’s team ran the day-to-day department operations.

“He lost control of this whole ship,” a source said of Banks as the power struggle continued in January.

Things came to a head between Sewell and Maddrey last month after she issued him a seven-day command discipline for abuse of authority after the Civilian Complaint Review Board sustained the allegations involving him over a voided gun arrest.

Sources say the commissioner was upset that her chief of department was appealing the discipline and that he had the backing of City Hall.

Adams publicly defended Maddrey, saying he was proud to have him as his chief of the department.

Sewell, unlike her predecessors, has also been required to get the mayor to approve promotions throughout the ranks.

Sources say she was denied a promotion for the cop who was running her office.

“Maybe there’s no good time, but there’s a right time to go if it’s true she’s running promotions through City Hall,” a source said. “It’s not normal.”

Additional reporting by Joe Marino