1995- as people have mentioned here and elsewhere before, the breakout of the SL war played a considerable part. It served as a big distraction for Gus and a lot of the NSW players. Gus later conceded he should've managed that series a lot better.
@King hit can go into more detail about that series. In 1996 with both sides SL-aligned players back, a stronger Blues team whitewashed a stronger Maroons team. A series where Gus epitomised "pick and stick" for eternity by keeping the exact same 17 for all 3 games.
2020- the same guy who wouldn't go near the Qld coaching gig back in 1995 after Wally got sacked, stepped up this time. If he really believed that Maroons team were as bad as a lot of people make out, I doubt he would've risked his reputation on them. 6 months later a stronger Qld line-up got belted (with all 3 games in Qld) under Slater's predecessor.
2025- a guy who looks like he's got the makings of being a genuinely decent coach, out-coached a guy who is clearly out of his depth. Much the same NSW squad 12 months previous looked the better team for 30 minutes in Game 1 despite being down a man, racked up a record halftime score in neutral territory in Game 2 and then won the game (and the mind-games) in Game 3. If Laurie Loser stays on for 2026 I could give you pick the margins for all 3 games because I've seen this show before. Saying that, I didn't think NSW would win in 2014 so there's always room for a surprise...
It's telling how a team's fortunes (even at Origin level where apparently the coach is just a talking head) change so notably with little more than a change of the coach.