AFC Wimbledon went into the final having twice shut out Notts County in the semi-finals and holding the best defensive record in the league having conceded 35 goals.
So when Hippolyte struck at the end of the first half, it was always going to take a mammoth effort for the Saddlers to find a way back.
In a rare moment of quality up to that point, Marcus Browne chested the ball down following a clearance from a corner and smashed a volley goalward.
The ball was blocked and came to Hippolyte, who struck it first time along the ground and into the bottom corner past Tommy Simkin.
Browne had earlier tested the Walsall keeper from distance, drawing a diving stop low to his left.
Wimbledon's heart-in-mouth moment came soon after the break as Walsall went in search of the equaliser, with Matt beating Owen Goodman to the ball and nutmegging the Dons keeper at his near post.
The Saddlers supporters willed the ball in as it trickled towards the line but defender Riley Harbottle got back to the line just in time to clear.
Simkin made an excellent late stop, saving Josh Neufville's near post shot with a strong left palm to keep Walsall in it.
But League Two's top attack, albeit with a lot of their goals scored during their incredible start to the season, ultimately could not penetrate the division's best defence.