Headline reductions “up to 40%” but most actually around 10-20%. Pretty standard click bait for this time of year. Summer stock coming in and need the space for it and next winters new colours already ordered.
As mentioned by someone else, it a symptom of consumerism in general. Difficult problem to solve. You need to order far in advance to get your product in time, but you still don’t know how much stock you will actually need so over order. Then you have to price in sale prices to ensure you make a profit on the batch as a whole. On top of this the general public love thinking they got a bargain. They’d rather buy a product marked down from £60 to £50 than an identical product being sold full price at £50.