Pope's decision was based on their belief that Pope's form and ability outweigh Hart's experience.
The West Ham United goalkeeper has struggled for form in recent seasons, most notably during his ill-fated loan spell at Serie A side Torino, and has made a series of high-profile errors during his time at the London Stadium.
Hart has endured a miserable campaign in the Premier League.
Their delight will contrast markedly with the disappointment of those missing out, with Hart - comfortably England's most experienced player - said to have missed the cut.
Southgate reveals his 23-man squad for the tournament in Russian Federation on Wednesday.
Midfielder Arfield swaps Burnley for Rangers
New Rangers manager Steven Gerrard hopes to emulate the style of football that Jurgen Klopp has established at Liverpool.
Pickford, by contrast, started every one of Everton's Premier League games as they finished eighth under former England manager Sam Allardyce.
"Gordon obviously is a Stoke man so I would expect him to back Jack but we have some very good goalkeepers", Southgate said.
What's your take? Let us know in the comment section below. Plus we have the likes of Fraser Forster and Tom Heaton, who is out injured, and there are other young goalkeepers coming through.
Swansea's Alfie Mawson will also not be included in Southgate's squad for the World Cup after he underwent successful knee surgery on Monday - keeping him out for between six weeks and two months.