OP is toying with us!

He was around, paying attention, seen that era back then! He knows!
Plus, there are lots of older threads of this. Very popular topic/subject (Nash/Dirk Mavs...SSOL Suns.... Nash Suns, etc)
But, ya. Pretty simple. Timing.
Late '90s. Nash was very young, the Suns team was good. But, not major contenders. They were bit of an older team. These were the post Barkley/Kevin Johnson/Majerle teams. 1st round exits in the playoffs.
After 2 season, traded to a bad, terrible, rebuilding, young Dallas team. (Mavs sucked the entire '90s, lottery teams...). They were the Washington Wizards/Detroit Pistons (for all yall younger Wiz/Pistons fans, look up them Mavs teams of the '90s also the Nuggets teams during the '90s, this should give yall hope in the future! lol) of today of the West during the '90s.
This is where/when Nash started gettin more playing time (later '90s). They stunk at drafting great players (minus Kidd). But, knew how to obtain great players (Dirk obviously, via trade with the Bucks....Michael Finley few yrs prior via trade , etc) 1st couple of seasons , The Mavs stunk under young Dirk/Nash. Aside from Finley, the Mavs weren't very good yet. Then they got a new owner (Mark Cuban) and things got better. They finally have a winning season, make the playoffs in 2001 (upset a veteran Jazz team in the 1st round). Lost to a strong veteran Spurs team in the next round. Problem was, the whole West got good as well during the 2000s. The Nash/Dirk teams normally lost in the playoffs to the Kings and Spurs (more veteran groups with good defense).
When Nash was traded back to the Suns in 2004. The Suns had to deal with the Spurs/Lakers/Mavs in the playoffs.
The Mavs and Suns were a fast paced offense, but tend to play little defense. Kings were fast paced offense as well, but played good defense. It was thei Mavs/Suns weakness in the playoffs. While older, veteran teams with good defense (Jazz, Kings, TWolves, Spurs, Lakers, Portland, Nuggets later on, Rockets, etc) . Sometimes injuries hurt the Mavs/Suns in the playoffs.
The Suns aged out by 2010/2011 ish and the dynamic group were traded away or left via FA. Phoenix declined.
Nash obtained by the Lakers via sigh and trade. As for the Nash/Howard/Kobe teams of the mid 2010s...... Lakers were old, banged up, so was Nash (injury prone at the time, bad back). Howard (traded by Orlando). Howard/Kobe chemistry was a disaster. and they both were dealing with their own injuries. Barely made the playoffs in 2013 as a 7th seed (45-37), swept by the Spurs in round 1. 2014, Lakers finished 27-55! Losing season/no playoffs. Nash missed most of that season, he retired after the season. Bad back.
Lakers went on to have 6 straight losing seasons/no playoffs. 2014-2019. The last Kobe years and post Kobe years. Even in Lebron's 1st season with the Lakers. Their worst stretch in their history. Similar to what the Spurs have been going through the past 5 seasons. Post Duncan years/Manu/Parker years.
So, ya. OP. Don't make us have to explain it to you again, you were there to witness it all or at least to have paid attention to it back then!

EDIT: As a Spurs fan, I would say that the suspensions (WCSF vs Spurs) did hurt the Suns chances for the title as well. Controversial.