I think it's a combination of all those things.
Autoglym is probably as good as it always was but the 'detailing' market has expanded massively and with it brought all kinds of new players. There's definitely a 'trend' element to it to as you only need to see how some of the newer stuff is branded and marketed, but that said I think there have been advances in chemical technology, certainly with respect to nano coatings etc. Has AG invested enough in these advances. I don't know but if not they are being left behind. It's not unusual for companies who have been market leaders, to rest too long on their laurels and be too slow to respond to changing markets. Before they know it, it's too late.
I've only ever used one Autoglym product - Fast Glass, which is excellent, but If they are losing their market share and drastically slashing prices, perhaps AG need to look at their image and do a bit of a rethink/refresh as they are possibly seen as very dated, even though the actual product may still be good.
