I agree with you in general and the Braves are a good example of why. As a Boston baseball fan I find it weird that the franchise in Atlanta technically owns ~80 years of Boston baseball history. In fact, the only Boston Braves World Series win happened at Fenway Park. But the Braves are practically forgotten in Boston sports lore. That history went to Milwaukee and Atlanta.
And while the banner for 1914 flies in Atlanta, the city has no cultural memory of it. To a Braves fan, it just represents something they did "back when they were in Boston." Just as Oakland has no cultural memory of Connie Mack. Meanwhile the Red Sox's exploits from around the same time are part of the ethos of the franchise, Dropkick Murphy's even made a song about the early 1900s Red Sox. The Miracle Braves of 1914 live nowhere. It's technically Braves history so the Red Sox aren't flying that flag. Their World Series win happened in Fenway Park but yet the park itself retains no memories of it. If the Braves had rebranded in 1953, the Sox might actually feel it's appropriate to celebrate their history.
The Braves date back to 1871 so 80 years of Boston baseball history is held in name only by a franchise down in Atlanta. Boston being the first (and longest) home of the longest continuously operating franchise in American sports is barely a footnote in regional history now.
Meanwhile in DC - the original and expansion Senators rebranded to the Twins and Rangers respectively so the Nationals fly the flag for the Senators' win in the 1920s and have statutes for Senators greats. While the Twins and Rangers claim the history of their respective Senators franchise, the Nats actually get to celebrate it at their ballpark. I just wish the Twins and Rangers had left the Senators history in DC so the Nats could actually claim to be a continuation of the two Senators franchises (and in turn leave the Expos history in Montreal).
And perhaps it's appropriate that the 1914 Philadelphia A's lost to the Boston Braves...
I can sympathize with Oakland's plight to a degree but Oakland fanbase is the last one who can pull the "we should keep the history" line. If the Braves ever left Atlanta and their fans pulled that ****, I would drive down to Atlanta myself and protest it. The fans in Oakland don't get to own Connie Mack, they don't get to own the most successful baseball team in Philadelphia's history, they don't get to own Chuck Finley's antics in Kansas City (as shameful as they were). The A's won 5 rings in Philly, the Oakland fanbase doesn't get to bitch their way into keeping that under and key.
I hate Yankees fans, but Oakland's fans are quickly becoming a close second. You don't get to not support your team and then cry like bitches when the owner decides to go elsewhere. Look at this:
https://www.baseball-reference.com/teams/OAK/attend.shtml. That team had abysmal attendance before John Fisher bought the team. They don't get to scapegoat John Fisher and pretend he's the reason you can't be bothered to support your team.
The Vegas experiment will almost certainly be a bust but at least the team will be away from a bunch of entitled bitches who couldn't be bothered to support the team and think they're entitled to a chunk of baseball history of two other cities.