If an idea is a good business opportunity, it's common for multiple people to be working on it independently at the same time. It's also common for many people to fail working on that very idea before you get to it.

One of the values of VCs and networks and experts is that they can tell you how other companies in your space have failed (running out of money, founder breakups, "people won't pay for it", "it really needs X but X doesn't scale", etc.).

If you watch the start-up space for long enough you start seeing multiple teams with the "same idea" but only a handful succeed at it; even at small a scale as university incubators.