Paetongtarn Shinawatra’s political rise was as rapid as her downfall.

Two years ago, she was a political novice running in her first election. Last August, she rose to become prime minister of Thailand. On Friday, a powerful court dismissed her from office for ethical breaches.

Ms. Paetongtarn’s political fortunes have always been tied to her father, Thaksin Shinawatra, a former prime minister who was ousted in a coup. Her appointment as prime minister appeared to be a stunning comeback for Mr. Thaksin. But that was possible, analysts say, only because Mr. Thaksin made a grand bargain with an old nemesis, Thailand’s royalist-military establishment.

Ms. Paetongtarn, 39, was considered a puppet of her father’s. Once she was in office, Mr. Thaksin started talking publicly about domestic issues like how to deal with President Trump’s tariffs and regional issues like the civil war in Myanmar. Eventually, he ran afoul of the old guard.

“He seems to have interpreted their deal to mean that ‘I get to be shadow head of government,’” said Michael J. Montesano, an expert on Thai politics at ISEAS-Yusof Ishak Institute in Singapore.

It ended with a body blow to the Shinawatra dynasty. Ms. Paetongtarn was the fifth prime minister linked to Mr. Thaksin to be removed by the Constitutional Court.

It was the latest instance, analysts said, of the old guard’s using the judiciary to neuter opponents. And it was further evidence, they said, that even though Thailand is a constitutional monarchy that regularly holds elections, it is beholden to an unelected royalist-military establishment.