1) It's not enough to have an amazing product that solves a dire need.
Let's dig into some examples.
He had competitors who also had forums. But again, easy entry conditions. You could post your same q on all the forums.
You basically have to get timing right -- when someone doesn't yet have software or is so fed up w/ a current solution
Such as startups.
In fact this was exactly @HubSpot's play -- go for smaller fish who don't use anything. Then grow w/ them.
If you go enterprise and are head-to-head w/ existing solns, then you need to be prepared for long sales cycles, constant follow up to get timing right.