You don't hang on to 4th WRs "just in case".
The Rams have guys well versed in their system in case of an injury to the top 3.
Besides, as Aly pointed out: no doubt VJ was not a happy camper. It was best to move on for all concerned.
At the same time, when a player has given you the amount of play that he has, it's not like he hasn't been worth his selection.
And, long draft history shows that 2nd round picks have about 1 in 4 chance of ever becoming a contributing NFL starter. He was a starter for awhile, was expected to be this year, but Nacua has caught the league by storm. There goes VJs spot.