Koeman has previously commented how much he likes the player.
To me, it's not so much of a panic buy, but more Koeman maybe switching plans on how he wants the team to attack.
I think initially, based on the first few games of pre-season, he was willing to try and build on the decent foundations RM had put in place attacking wise, and then sort out the defence as a priority.
However, I think he's realised that we've become a bit stagnant, with a lot of our attacking players being very similar in terms of style, and we tend to overplay - this being incredibly evident in the Espanyol game.
That to me is why he's changed tact and prioritised Bolasie, as a player who brings something different to what we already have.