It's not simple failure to get high enough. That was not the fatal mistake. It's multiple mistakes, the accumulation of which results in no more choices. Poor flight planning, possibly an inhibition of an ATP to ask "lower ranked" local pilots about various routes, and waiting too long to abort. They lacked an abort plan. They could not have been asking "what do I do right now if the powerplant fails?" Because they not only accepted going passed the point of managing a powerplant failure, to the point where they had no options even with a fully operating powerplant. There was nothing wrong with that airplane. It was all errors in judgement that lead to no choice but a crash.

Having flown in and out of Aspen many times myself, I have never used Independence pass. I've opted for the down valley northwest route for climb out, then north, and finally east to Corona/Rollins pass. Many choices before, during, and after pass crossing. A local pilot would have given alternatives to Independence, and their reasoning. A local flight instructor would have reminded them about density altitude, leaning, and even the option of not taking off fully fueled in order to improve climb performance, and fully fuel on the other side of the mountain range instead.

Colorado sees this same lack of awareness of the effects of altitude with hikers all the time too. Folks from New York and Florida and California, regularly climb 14ers in fall and unwittingly get stuck in snow storms while Denver is clear as a bell, having no imagination at all for treachery. And their families are appalled when the search and rescue is called off because it's even too treacherous for S&R operations. Happens every year.

You can't fight physics. Normally aspirated planes are seriously underpowered at high altitude. It's shocking. And they don't have much excess power to start with.

This pilot made a fatal mistake much earlier than the actual accident by not becoming deeply uncomfortable at the low altitude perniciously taking away all options. He assumed the rate of climb would get them over the pass. A small tailwind makes this even worse as it reduces the time you gave for climb.

Every time I fly in the mountains I see planes well below my altitude, thousands of feet. I've slowly build up a store of power and thus choices, including more time to troubleshoot, more time to announce position which is a line of sight transmission.