How Shahrukh khan became the King of Bollywood?

Everyone else has already mentioned the general answers, hard work and dedication, but just to fill int he specific gaps, he was a middle-class Delhi boy who joined Barry Johns acting workshop in Delhi while he was in college, the same place where Kunal Kapoor, Varun Dhawan, and dozens of others were trained. He acted in plays and an art film, In Which Annie Gives It Those Ones, through Barry John’s troupe. And the connections he made led him to be cast in Fauji, a TV serial being filmed in Delhi.

He was exceptional in Fauji, not only charming the audience with his performance, but charming the producer and director with his dedication to the work, showing up early and staying late and memorizing not just his lines but the entire script. Because of Fauji, he was offered two other serials, Circus and Idiot, to be filmed in Bombay.

In Bombay, he continued to do good work and make a good reputation for himself, finally being offered his first film, by Hema Malini, Dil Aashna Hai. Shortly afterward he was offered two others, Deewangee and Chamatkar. All 3 films released in 1992, Dil Aashna Hai was filmed first but came out after Deewangee. In all 3 films he wasn’t the standard lead, only appearing in the second half of Deewangee, playing second fiddle to the heroine in Dil Aashna Hai, and coming in second to the character actor Naseeruddin Shah in Chamatkar. But his performances were charming and, again, he had a good reputation on set. He was also amusing and charismatic in the interviews and public appearances surrounding the releases.

After 1992, he continued to be offered work by many producers and directors, and he continued to take “different” kind of roles, doing an art film re-interpretation of Madame Bovary (Maya Memsaab) or taking the villain’s role in Baazigar, Darr, and Anjaam. His work on Darr brought him to the attention of Yash Chopra and his son Aditya, and Aditya convinced him to take the part in DDLJ, even though it was the kind of simple love story he had been trying to avoid.

After DDLJ, he became one of the top stars of the industry, delivering hit after hit through out the 90s. He made the movie Baadshah and started using that nickname for himself in interviews, and it was picked up by the press.

Now, while Aamir Khan has slowed down and focused on making only a few high quality films, and Salman Khan has solidified his fanbase at home, Shahrukh is the only one who is focused on the overseas market and on building his “brand”. Therefore, while he may not be the most powerful or popular star (how would you even measure that?), he is certainly the one most focused on “ruling” the industry.