Alternatively the established players have become
incredibly good at what they do - it's simply something different. Elon is motivated ideologically by a desire to colonize Mars. By contrast this [1] is the current head of Lockheed Martin, this [2] was the head of Boeing until 2015 when it became clear they were losing by most of every metric to SpaceX. Exact same story in both cases: 0 tech background + MBA.
These people are not aiming to achieve anything, just to make more money in general, and specifically to extract more taxpayer money. And they are extremely good at that. For instance ULA (an anticompetitive joint venture between Boeing/Lockheed) managed to get the government to pay them $422 million per rocket launch. [3] The only reason this ended was because of those pesky kids, SpaceX in this case - who are charging $83-$97 million for a comparable launch capability. And that's at the inflated government price - private commercial launches go for about $65 million. SpaceX have a big picture goal. Boeing/Lockheed exist only to make more money.
Perhaps my favorite example of ULA's success is the 'launch assurance capability subsidy.' ULA managed to get the government to give them about $1 billion of taxpayer money per year, to do literally nothing but exist. [4] Elon's taken flak because of astroturfed articles suggesting he feeds on government subsidies when they tend to be little more than tax rebates (in other words the government taking less). But this is literally getting the government to write you a check for $800 million, just to make sure you have your vehicles ready to accept their $420 million check later on. ULA, for their part, refers to it as an "innovative contracting mechanism." Whatever it is, getting the government to spew taxpayer money to you is what they're trying to do, and yeah - again, they are very good at it.
The examples are endless here. For instance Lockheed Martin is also behind the maligned F-35 program (works out to an average of about $29 billion a year of taxpayer money, for the next 50 years), the SLS launch vessel, perpetually 3 years out on the horizon, draws billions per year and a large chunk of NASA's entire annual allocation, so forth and so on.
[1] - https://en.wikipedia.org/wiki/Marillyn_Hewson
[2] - https://en.wikipedia.org/wiki/James_McNerney
[3] - https://arstechnica.com/science/2017/06/air-force-budget-rev...
[4] - https://spacenews.com/u-s-air-force-looks-at-ending-ulas-lau...