Why were the two major candidates in 2000 unchallended?

[buritobr]

In 2000, the primaries were very easy for Al Gore and George W Bush. Bill Bradley was no serious threat to Al Gore. John McCain was no serious threat to George W. Bush. Why was so easy?

Usually, vices of two term presidents become nominees. But there was some challenge for George H Bush in 1988.

[OSR stands with Israel]

McCain was a serious threat to W Bush, it was just after being smeared in SC his campaign collapsed.

[NCJeff]

Bush consolidated donor support early on.  Remember, small donor (and online) fundraising wasn't the norm until later election cycles.

That said, there were other possible contenders.  Based on the polling here (https://en.wikipedia.org/wiki/2000_Republican_Party_presidential_primaries) the OP's question is probably best re-framed as: why did Elizabeth Dole drop out?

[darklordoftech]

There was a lot of political apathy and a feeling that there were no real issues left and that the parties were “tweedledee and tweedledum”. This is in contrast to 2004 (Iraq War), 2008, (Iraq War and the recession), 2012 and 2016 (Republicans energized by hatred of Obama) and 2020 (Democrats energized by hatred of Trump).

[Redban]

McCain gave Bush some trouble in 2000. There were some infamous attack ads. He wasn't unchallenged.

[morgankingsley]

Al gore is easy, he was the sitting vice and that meant a lot more back then

Bush was a successful governor and the son of a former president, so people thought he would be a recipe for success