Products being recognised better than keywords

[cb83tv]

We have a website that hasnt been changed in a while, but was doing quite well anyway, it suddenly went up in google for no reason but we're not complaining :o)

now if you search for a specific product our site is no. 1 for it , even better than the manufacturers, but if you search for our keywords we aren't, the product is one of our most expensive ones so its a good thing but i cant understand why our site is no.1 for it, can anyone explain it please?

Thanks in advance