(CNN) He was at the pinnacle of politics -- the man who led a political novice to the Republican presidential nomination.

Corey Lewandowski seemed virtually invincible for much of Donald Trump's campaign. Trump, the presumptive GOP nominee, has repeatedly stood by his aggressive and controversial campaign manager through crises that would have ended the career of virtually any other political operative.

The bond between the two was so strong that Trump quickly dismissed talk of firing Lewandowski after he was arrested in March and charged with simple battery of former Breitbart reporter Michelle Fields. (The charges were later dropped.)

But by Monday, it became clear that Lewandowski had finally overplayed his hand when Trump abruptly fired him

JUST WATCHED Corey Lewandowski's full CNN interview with Dana Bash Replay More Videos ... MUST WATCH Corey Lewandowski's full CNN interview with Dana Bash 28:51

Interviews with multiple campaign officials, party strategists and sources in Trump's inner circle reveal that Lewandowski's ouster — as dramatic as it appeared — was a long time coming. For months, tension had been building within the Trump campaign and small circle of advisers. Simultaneously, a quiet campaign to convince the New York billionaire to cut Lewandowski loose was gaining traction.

The breaking point: Lewandowski had gone one step too far by targeting Trump's family.

The relationship between Lewandowski and Jared Kushner, the husband of Trump's daughter, Ivanka, grew increasingly strained.

Rumors that Lewandowski had attempted to plant negative stories in the press as part of a broader strategy to "take Jared down" sealed Lewandowski's fate, sources said.

Multiple sources told CNN that Ivanka Trump and Kushner were central to Donald Trump's ultimate decision to fire Lewandowski. Trump's children had attempted for months to persuade their father to let his campaign manager go. They worried that Lewandowski was becoming an increasingly toxic influence on Trump, stoking some of the billionaire's worst instincts rather than keeping them in check ahead of the general election.

Trump's children watched with frustration as Trump, now the newly minted GOP nominee, dug himself deeper and deeper into a hole. To the outside world, Trump appeared unaware of — or worse — at times even uninterested in, the grave political consequences of his actions.

The candidate repeatedly targeted U.S. District Judge Gonzalo Curiel, questioning Curiel's ability to make fair legal rulings because of his Mexican heritage. Following the Orlando massacre that killed 49 people, Trump took to the podium to imply that President Barack Obama might have somehow been complicit in the mass shooting. He also doubled down on his call for a ban on Muslims from entering the United States, drawing near unanimous criticism from fellow Republicans.

Lewandowski declined to acknowledge the turmoil with Trump's family, even after it was described to CNN by multiple sources. Just hours after being fired, Lewandowski told CNN's Dana Bash that he has had a "great relationship" with the Trump family and no motivation to smear any of Trump's allies.

"If Donald Trump wins, that's good for Corey Lewandowski and good for the country," he said. "Why would I want to do anything other than what's in the best interest of him and the campaign?"

While Lewandowski insisted Monday that he had no regrets about the way he conducted himself as campaign manager, it's unclear what place Lewandowski might have in the future of GOP politics.

A former officer trainee in the New Hampshire marine patrol who had never run a presidential campaign before, Lewandowski in many ways isolated himself from the national Republican Party throughout the 2016 campaign. He is viewed as having refused to heed concerns from GOP leaders that Trump's candidacy -- particularly his rhetoric about immigrants and minorities -- is inflicting permanent damage to the party's image.

Lewandowski's reputation has also been tainted in other ways: His arrest raised questions about his temperament -- and that of Trump -- even though the charges were dropped.

As he exits the Trump campaign, Lewandowski's political legacy is that he was a leading architect behind a deeply divisive presidential campaign that seized on anger and frustration across the country in an unprecedented way. Of course, Trump also defied expectations and smashed the competition.

For now, many close to Trump are privately sharing a sense of relief, and hope Lewandowski's departure will mark a significant campaign reset. For at least one Trump adviser, the celebration was not so private.

Trump adviser Michael Caputo tweeted Monday: "Ding dong the witch is dead!"

By mid-afternoon, Caputo, too, was gone from the campaign. He expressed regret for the comment and stepped down from his position at the Republican National Convention.