LBJ refused to run after leading in the primaries

That is more than a little bit misleading

LBJ faced long odds in November; his top aides feared that he might not even win re-nomination. With his public approval rating at around 36 percent, LBJ had barely survived a surprisingly strong primary challenge from antiwar Sen. Eugene McCarthy in New Hampshire, who took 42 percent of the vote to LBJ’s 48 percent on March 12. Four days later, on March 16, New York Sen. Robert F. Kennedy, a long-time LBJ nemesis, declared that he, too, would challenge Johnson for the nomination

…

On March 31, 1968, Lyndon B. Johnson appeared on national television and announced … that he had decided not to seek his party’s nomination for president.

[Quotes reordered from how they were in the source for better clarity]

https://web.archive.org/web/20240710212846/https://www.history.com/news/lbj-exit-1968-presidential-race

Better source with lots more details (which makes it harder to excerpt) - https://web.archive.org/web/20240710213056/https://www.npr.org/2018/03/25/596805375/president-johnson-made-a-bombshell-announcement-50-years-ago

An open convention was held in Chicago with rioting in the streets.

A note about those riots -

On September 4, 1968, Milton Eisenhower, chair of the National Commission on the Causes and Prevention of Violence, announced that the commission would investigate the violence at the Chicago convention and report its findings to President Lyndon Johnson.[3][36] A Chicago lawyer, Daniel Walker, headed the team of over 200 members, who interviewed more than 1,400 witnesses and studied FBI reports and film of the confrontations.[36] The report was released on December 1, 1968, characterized the convention violence as a “police riot” [37] and recommended prosecution of police who used indiscriminate violence; the report made clear that the vast majority of police had behaved responsibly, but also said that a failure to prosecute would further damage public confidence in law enforcement.[36] The commission’s Walker Report, named after its chair Daniel Walker, acknowledged that demonstrators had provoked the police and responded with violence of their own, but found that the “vast majority of the demonstrators were intent on expressing by peaceful means their dissent”.[4]: 3

[Bolding added]

https://web.archive.org/web/20240710214549/https://en.wikipedia.org/wiki/1968_Democratic_National_Convention_protests

He lost to Nixon who said he had a secret plan to end the war. But, of course he lied.

This is completely correct, but just saying he lied is kinda understating the magnitude of the horrifying things he and Kissinger did in that region of the world. A small sample - https://web.archive.org/web/20240710215210/https://theconversation.com/henry-kissingers-bombing-campaign-likely-killed-hundreds-of-thousands-of-cambodians-and-set-path-for-the-ravages-of-the-khmer-rouge-209353

Incidentally, as long as I’m thinking about the terrible things the 1968 election led to, its worth pointing out that Nixon’s use of law and order rhetoric brought the Dixiecrat segregationists who were big mad about the civil rights acts fully into the Republican party, who was then able to spend the 1970s dismantling lots of integrative programs and throwing black people into prison for bullshit reasons (like, this is the moment mass incarceration takes off). It’s also worth pointing out how a lot of people just remember Humphrey as a spineless Johnson lackey who kept supporting his boss’s war even though he really didn’t agree with it, but we should remember him as the badass who walked into the 1948 Democratic national convention and said it was time to drop segregationist bullshit and start promoting civil rights.

I imagine we disagree on why it turned out how it did, but I imagine we agree that the world would have been a lot better place if Nixon lost the 1968 election.