This was not a move by Biden to position Kamala for a loss, but he certainly did not want Pelosi and the Democratic establishment to gloat on a win. Which is why he immediately endorsed Kamala for the presidency, right after announcing he was stepping down from the race.

> https://www.youtube.com/watch?v=O9fSK2AR594

Pelosi suggested there should have been an open primary after Biden dropped out. But Biden's endorsement ensured that they could not backtrack from Harris.

https://edition.cnn.com/2024/08/15/politics/joe-biden-legacy...

Selection as VP doesn't mean by default that the running candidate/party endorses the candidate. Most often, VPs are chosen because they are harmless enough to become opposition to them, as a concession to a former opponent, or in most cases to bridge the demographic gap and reach out to a particularly marginalized segment of voters who are not adequately represented in governance.

> she was a incredibly obvious choice and would have had a very strong likelihood of getting the nod had there been actual primaries.

Lol, hell no. She already lost the primaries multiple times. She was extremely unpopular. In the 2020 elections, running with Biden helped boost her profile slightly, but back then Biden was a much more stronger candidate and his choice of running mate wouldn't have mattered - Trump was extremely unpopular then.