I think it's a US thing though. Obviously I know that in US English the word has both meanings, but in the UK a troll is something that hides under a bridge, and the fishing is trawling.

Took me a while to figure out the humour inherent in the double meaning when I first came across it (in the 90s)

I always thought trawling involved dragging a net whereas you trolled with a lure (enticing fish out to chase it).

e.g., you might trawl for prawns but troll for snook.

Never heard that in UK english.

I just assumed that with an american accent the words sounded the same so people stopped using 'trawl'... I've been wrong before though.

I can confirm that this is not the case; trawl and troll shouldn't rhyme any more than Paul and pole, tall and toll, fall and foal, etc.