Final answer:
George Harrison released the successful triple album 'All Things Must Pass' following the Beatles' breakup in 1970.
Step-by-step explanation:
Following the Beatles' breakup in 1970, the former band member who soon released a successful studio recorded triple album as a solo artist was George Harrison. His album, titled All Things Must Pass, is widely regarded as one of the best solo works produced by any of the ex-Beatles. The album includes hits like My Sweet Lord and the title track All Things Must Pass, showcasing Harrison's deep spirituality and maturity as a songwriter.