"We are not an organisation with the luxury of a lot of resources around us," said De Bruyn.
"I've got 18 players to pick from in my national squad and I know what they've put in for the last three years.
"It sounds like a cliche that the hard work has paid off, but it certainly did and I’m really ecstatic for the players."
On Friday, Namibia chased down their modest target of 126 with skipper Gerhard Erasmus making an unbeaten 53.
"We are a small country, a small number of people play cricket. We should be proud of ourselves," said Erasmus.
Namibia finished behind Sri Lanka in Group A after the 2014 champions dismissed the Netherlands for just 44, the second lowest total in tournament history, for an eight-wicket win.
Sri Lanka will be grouped with England, Australia, South Africa, defending champions West Indies and Bangladesh in the Super 12.
"We are ecstatic, I've got to remind myself what just happened out there, but it has happened to a really good group of people," added De Bruyn.
"It's time for us to reflect and also enjoy this moment, but we certainly didn't come here to go and lie down now.
"Facing India, Pakistan and New Zealand, those types of teams, is going to be a great experience for these players but we want to be competitive in whatever we do, with ball, bat and in the field.
"The way we present ourselves, we are going to compete, and we are looking forward to that."
Erasmus hit three boundaries and a six in his 49-ball innings while David Wiese, who played for South Africa at the 2016 World Cup, was undefeated on 28.
"I count on my senior men to stand up when the pressure is on. And two of us did it tonight. Hopefully we can do it through the tournament," said Erasmus who put on 53 for the third wicket with Wiese.
Wiese smashed two sixes and a boundary in a 14-ball innings which was a whirlwind in comparison to Namibia's sedate early progress.
They were only on 49-1 at the halfway stage although, ultimately, Zane Green's 24 off 32 balls and Craig Williams's 15 from 16 deliveries proved to be an ideal foundation on a desperately slow surface.
"It's completely overwhelming," said Wiese who had also taken 2-22.
Ireland had appeared well set at 71-2 at the midway point of their innings but the runs dried up as Namibia's bowlers turned the screws, restricting their opponents to 125-8.
Openers Paul Stirling and Kevin O'Brien gave Ireland a flying start.
They put on 67 before Stirling fell to left-arm finger spinner Bernard Scholtz in the eighth over.
Stirling made 38 with five fours and his team's only six while O'Brien hit 25.
Ireland skipper Andy Balbirnie contributed 21 before he fell to seamer Jan Frylinck attempting to force the pace.
Only 54 runs came off the last 10 overs with Ireland's next seven batsmen all failing to reach double figures.
Frylinck finished with 3-21.
As well as securing the last place in the Super 12 stage, Namibia are also guaranteed a spot in the 2022 tournament in Australia.