What happened to Bitcoin Core v0.20.1?
Are you sure you actually installed 0.20.1 before? It seems that the pull request to add the 0.20.1 release to bitcoin.org never got merged: https://github.com/bitcoin-dot-org/Bitcoin.org/pull/3435
If you look on the project's own site, https://bitcoincore.org, you'll see that 0.20.1 is available just fine.
I would be very surprised if anything at all changed regarding block chain synchronization in 0.20.1 vs 0.20.0. I suspect what happened is that your node initially just picked bad peers to synchronize from, but after (re)installing 0.20.0, that went away on its own.