The PSC is back, but it's a different party.
Back in 1999 and 2003 elections, when the PSC was the leading party in popular vote under Pasqual Maragall (CiU won more seats due to malapportionment), 30% of its base had a predominantly Catalan identity ("more Catalan than Spaniard")
The 2021 PSC under Salvador Illa has lost 2/3 of the catalanist base: only 10% identify as "more Catalan than Spaniard".
The catalanist middle-class has turned to sovereigntism since 2010
To what extent have the PSC taken most of the C’s voters from the last election? The map would suggest that this is basically what has happened (although the ERC has also been able to gain some coastal areas which voted C’s last time).