The common denominator between the Monkees and the Archies was Don Kirshner.
Per Wikipedia:
"In the early 1960s, Kirshner was a successful music publisher as head of his own company, Aldon Music, which later was sold to Screen Gems-Columbia Music. With Al Nevins, Kirshner brought performers such as Bobby Darin together with songwriters and musicians. He'd later became president of COLGEMS, a subsidiary of the COLPIX label, in 1966.
Kirshner was hired by the producers of
the Monkees to provide hit-worthy songs to accompany the television program, within a demanding schedule. Kirshner quickly corralled songwriting talent from his
Brill Building stable of writers and musicians to create catchy, engaging tracks which the band could pretend to perform on the show. This move was not because of any lack of the Monkees' talent but was required in order to keep up with the demanding schedule to churn out ready-to-go recordings to give each week's episode its own song. While
Mike Nesmith and
Peter Tork were already experienced musicians – and
Davy Jones was an established musical performer – as a working band, they had little experience; and
Micky Dolenz was completely new to drums. Each Monkee was retained for vocal duties but they did not actually play instruments on the records.
The formula worked phenomenally well – the singles "
Last Train to Clarksville", written by
Tommy Boyce and Bobby Hart, and "
I'm a Believer" and the first two Monkees albums were produced and released in time to catch the initial wave of the television program's popularity. The lead guitar on "Last Train To Clarksville", "
Valleri" and the Monkees theme was written and played by Louie Shelton. After a year, the Monkees wanted a chance to play their own instruments on the records. They also wanted additional oversight into which songs would be released as singles. Further, when word belatedly came out that the band had not played on the first season's songs, a controversy arose, and the public expressed a desire to hear the television stars perform their own music."
Kirschner essentially did the same thing with the Archies, except that he took on the producer role as well. He avoided the talent/ego/personality conflicts that he'd had with the Monkees by hiring studio musicians to make the music and having the series star cartoon characters. Boom, no more conflicts. If someone got too cocky about being the "star" they could be fired and replaced. This made things much easier for the producer.
Kirschner later did "Ic Concert", then "Don Kirschner's Rock Concert" as well as being music supervisor for a number of TV series and movies and running record labels.