Answer by taking a quote from the following article:

Allen Toussaint (; January 14, 1938 - November 10, 2015) was an American musician, songwriter, arranger and record producer, who was an influential figure in New Orleans R&B from the 1950s to the end of the century, described as "one of popular music's great backroom figures." Many musicians recorded Toussaint's compositions, including "Java", "Mother-in-Law", "I Like It

In 1960, Joe Banashak, of Minit Records and later Instant Records, hired Toussaint as an A&R man and record producer. He also did freelance work for other labels, such as Fury. Toussaint played piano, wrote, arranged and produced a string of hits in the early and mid-1960s for New Orleans R&B artists such as Ernie K-Doe, Chris Kenner, Irma Thomas (including "It's Raining"), Art and Aaron Neville, the Showmen, and Lee Dorsey, whose first hit "Ya Ya" he produced in 1961.  The early to mid-1960s are regarded as Toussaint's most creatively successful period. Notable examples of his work are Jessie Hill's "Ooh Poo Pah Doo" (written by Hill and arranged and produced by Toussaint), Ernie K-Doe's "Mother-in-Law", and Chris Kenner's "I Like It Like That". A two-sided 1962 hit by Benny Spellman comprised "Lipstick Traces (on a Cigarette)" (covered by the O'Jays, Ringo Starr, and Alex Chilton) and the simple but effective "Fortune Teller" (covered by various 1960s rock groups, including the Rolling Stones, the Nashville Teens, the Who, the Hollies, the Throb, and ex-Searchers founder Tony Jackson). "Ruler of My Heart", written under his pseudonym Naomi Neville, first recorded by Irma Thomas for the Minit label in 1963, was adapted by Otis Redding under the title "Pain in My Heart" later that year, prompting Toussaint to file a lawsuit against Redding and his record company, Stax (the claim was settled out of court, with Stax agreeing to credit Naomi Neville as the songwriter). Redding's version of the song was also recorded by the Rolling Stones on their second album. In 1964, "A Certain Girl" (originally by Ernie K-Doe) was the B-side of the first single release by the Yardbirds. The song was released again in 1980 by Warren Zevon, as the single from the album Bad Luck Streak in Dancing School it reached 57 on Billboard's Hot 100. Mary Weiss, former lead singer of The Shangri-Las, released it as "A Certain Guy" in 2007.  Toussaint credited about twenty songs to his parents, Clarence and Naomi, sometimes using the pseudonym "Naomi Neville". These include "Fortune Teller", first recorded by Benny Spellman in 1961, and "Work, Work, Work", recorded by the Artwoods in 1966. Alison Krauss and Robert Plant covered "Fortune Teller" on their 2007 album Raising Sand.

what did he do that was successful during that time?
Notable examples of his work are Jessie Hill's "Ooh Poo Pah Doo" (written by Hill