Pretty interesting article here from the BBC on why Columbo is still popular half a century after it premiered on American TV - and why it still draws new fans:

Even 50 years since its first season began on 15th September 1971, Columbo remains a TV show like no other. The US series with Peter Falk in the title role - as the ramshackle, eccentric, cigar-chomping, raincoated LAPD homicide detective Lieutenant Columbo - revolutionised what a cop show could be. Here was a murder mystery where the murder was no mystery: audiences saw the deadly deed at the start of each episode, invariably carried out by one of LA’s rich and famous in an attempt to preserve their esteemed reputation.

It left the rest of the show not as a “whodunnit” in the vein of Agatha Christie, but a “howcatchem”, with the unassuming, amiable yet sharp-witted Columbo working to unpick the killer’s “perfect” alibi one seemingly insignificant clue at a time - shoelaces, caviar, air conditioning - before bringing down their arrogant conceit with a final piece of incriminating evidence in a thrilling “gotcha!” moment that Falk himself referred to as the “pop”. Columbo’s methods often involved elaborate set pieces where traps were set for the murderer (planting a false address of a suspect knowing the killer would try to frame him; asking a man to pretend to be his blind brother to break an alibi) that were dramatic, cathartic finales (even if the charges wouldn’t always necessarily stand up in a court of law).

bbc.com