When it comes to signing the best players in the world, our position is that we are more likely to sign a world class player before they become world class. You've obviously got to identify and develop and get some luck on route. If he stars at Anderlecht, we would have been looking at a fee 5x more next summer and far more competition.
He was prolific last season for a unfavoured team and the best team in league are taking him on loan for next season. Can't recall too many times where that has happened. Anderlecht sold Tielemans for a decent amount so it's not like they are desperate to borrow someone.
Generally the best clubs don't really want loans, as it's developing a player you don't own, it's more of a stop gap or a bit of extra cover. But you'd imagine he will get game time, otherwise why are Anderlecht keen and why would we loan him to them.