Frank Vincent Zappa (December 21, 1940 - December 4, 1993) was an American musician, composer, activist and filmmaker. His work is characterized by nonconformity, free-form improvisation, sound experiments, musical virtuosity, and satire of American culture. In a career spanning more than 30 years, Zappa composed rock, pop, jazz, jazz fusion, orchestral and musique concrete works, and produced almost all of the 60-plus albums that he released with his band the Mothers of Invention and as a solo artist. Zappa also directed feature-length films and music videos, and designed album covers.

Zappa and the Mothers of Invention returned to Los Angeles in mid-1968, and the Zappas moved into a house on Laurel Canyon Boulevard, only to move again to one on Woodrow Wilson Drive. This was Zappa's home for the rest of his life. Despite being a success with fans in Europe, the Mothers of Invention were not faring well financially. Their first records were vocally oriented, but Zappa wrote more instrumental jazz and classical oriented music for the band's concerts, which confused audiences. Zappa felt that audiences failed to appreciate his "electrical chamber music".  In 1969 there were nine band members and Zappa was supporting the group himself from his publishing royalties whether they played or not. 1969 was also the year Zappa, fed up with MGM Records' interference, left them for Warner Bros. Records' Reprise subsidiary where Zappa/Mothers recordings would bear the Bizarre Records imprint.  In late 1969, Zappa broke up the band. He often cited the financial strain as the main reason, but also commented on the band members' lack of sufficient effort. Many band members were bitter about Zappa's decision, and some took it as a sign of Zappa's concern for perfection at the expense of human feeling. Others were irritated by 'his autocratic ways', exemplified by Zappa's never staying at the same hotel as the band members. Several members played for Zappa in years to come. Remaining recordings with the band from this period were collected on Weasels Ripped My Flesh and Burnt Weeny Sandwich (both released in 1970).  After he disbanded the Mothers of Invention, Zappa released the acclaimed solo album Hot Rats (1969). It features, for the first time on record, Zappa playing extended guitar solos and contains one of his most enduring compositions, "Peaches en Regalia", which reappeared several times on future recordings. He was backed by jazz, blues and R&B session players including violinist Don "Sugarcane" Harris, drummers John Guerin and Paul Humphrey, multi-instrumentalist and previous member of the Mothers of Invention Ian Underwood, and multi-instrumentalist Shuggie Otis on bass, along with a guest appearance by Captain Beefheart (providing vocals to the only non-instrumental track, "Willie the Pimp"). It became a popular album in England, and had a major influence on the development of the jazz-rock fusion genre.

why did he think the band lacked effort?
some took it as a sign of Zappa's concern for perfection at the expense of human feeling.