Why did kennedy choose lyndon b. johnson to be his running mate

"Kennedy chose Senate Majority Leader Lyndon B. Johnson, who had finished second on the presidential ballot, as his running mate. Johnson, a Protestant Texan, provided geographical and religious balance to a ticket led by a Catholic Northeasterner, but many liberals did not like the pick"

found this info from (https://en.wikipedia.org/wiki/1960_Democratic_Party_vice_presidential_candidate_selection)

The primary reason that John F. Kennedy chose Lyndon B. Johnson as his running mate is that Kennedy was seen as young and inexperienced while Johnson was a so called "Master of the Senate" that had served as a member of the House and Senate. Johnson also balanced out Kennedy's New England background with a dose of Texas.

In many ways, it is similar to Barack Obama choosing Joe Biden, although Obama treated Biden more as an equal while Kennedy isolated Johnson.