Selling Vinicius would be a "smart" move, and not like they would even need to get any new player neither, they can put Mbappe on left, and Endrick on the striker and I bet you that they would still be strong enough to win the league that way. And they can make 150+ million euro from just selling Vinicius as well, so it's all possible.
One thing they are not doing it for, is that it's very hard to sell your best player, and Vini is either their best player or second best if you count Mbappe as best, and selling him would be a very hard deal. They would rather check out and see if they could make it work with him on the field, they would sell him as a last resort. That won't happen this summer, they need to wait one more year for that.
It is quite impossible to combine Vinicius with Mbappe well so one of them must leave the club and between these two star players, Vinicius is possibly a player who will be sold by Real Madrid. They just got Mbappe in the last summer and has no reason to let him going away, so Vinicius will be their only choice.
However, Real Madrid know that Vinicius is a star player with important role in their club recent seasons and they only can sell Vinicius after finding a good replacement of this Brazilian player. Perhaps a replacement has less brightness and transfer value than Vinicius, but an important thing he must have is a different favorite position and playing style compares to Vinicius.
Rumor is Real Madrid will sell Rodrygo in this summer and very likely Vinicius won't leave in this summer. If they sell him, they will only do it in a next summer market next year but as said they must prepare good replacements of Vicinius.