I'm not sure that this was all "Corbett struggling at center, better get Allen in there" type of decision whatsoever.
The LA Rams pulled starting RG Austin Corbett to OC to replace Austin Blythe and then promoted Bobby Evans to RG to replace Austin Corbett. If either Corbett or Evans struggles, then they have to undo those decisions.
The Rams had one vacancy on the offensive line, but made decisions to try to new interior offensive linemen. That was what they did in 2019 (bad results).
I hope that by restoring Corbett to RG, the Rams can focus on finding the best center, whoever that may be. Right now, it's Brian Allen