Which sentence is correct and why?
The World Cup is held every four years.
or,
The World Cup is being held every four years.
Which sentence is correct and why?
The World Cup is held every four years.
or,
The World Cup is being held every four years.
The first is correct since the World Cup competition is a very well-established and long-standing practice.
'US Presidential Elections are held every four years'
But you might say 'Committee meetings are now being held once a fortnight', let's say, instead of once a month or something. But once they get established you would probably revert to '...meetings are held once a fortnight'. The inclusion of 'being' suggests an unusual or provisional arrangement.
"The world cup is held every four years" is a statement of fact. "The world cup is being held every four years, however, implies that it is held every four years at the moment, but the speaker/writer would go on after a comma or semicolon to modify this by saying it would be held at a different interval in the future.
The first sentence is the most common and the one that makes most sense.
Google produces "World Cup is held every four years" about 706,000 results. Note the use of inverted commas, the entire phrase/clause being searched is one item.
Conversely for "World Cup is being held every four years" produces only six results which includes the OP's post.
The present progressive/continuous tense is primarily used to expresses ongoing or incomplete actions and situations which are temporary. The same rules apply when we use the passive voice.
The present progressive is not used to talk about permanent situations, or about regular happenings or habits. For these we use the present simple tense.