Jay Jaffe’s column at Baseball Prospectus sums it up best:
First baseball tried to drive out Robinson, and it failed to integrate all teams for years. Then it kept subtle limits on how many blacks could be on a team, and how many could be on the field at one time. Then it said that they couldn’t be managers or general managers. On April 10, 1947, though, when Branch Rickey issued a press release that said, simply, “The Brooklyn Dodgers today purchased the contract of Jackie Roosevelt Robinson from the Montreal Royals. He will report immediately,” when Robinson played against the Braves at Ebbets Field in the season opener on April 15, all the promises—the unalienable rights, the reward of hard work, America itself—came true. In that moment, there was equality of opportunity.