Twitter isn't the only idiocy Musk is in the news for today. The defense of the compensation package is preposterous, but that's not the craziest thing in there. The last line of the article is revealing:
"Musk last year that he would be surprised if the company had not put a person on Mars by 2026. As of this writing, however, SpaceX has yet to send a person beyond Earth’s orbit."
Now, let's talk about launch windows for a minute. Earth and Mars both orbit the sun. If you want to throw something from here to there, you do it when the position of the objects is such that the trajectory is as short as possible, given how fast your rocket travels. Planets move fast. If your rocket travels really fast (think Star Trek sublight speeds), this is fairly irrelevant. Our rockets don't travel that fast, and fuel is finite. You need a
much bigger rocket if you want to throw a manned lander to Mars when the objects are far apart. You have to lift all that extra fuel you added to get free of the Earth's gravitational field, plus the extra food for the crew, plus you have to design the thing. All of that costs, so in practice we don't do this.
The rotation of the Earth and Mars is such that launch windows occur about every two years. We just missed the most recent one, so the next opportunities are in 2024, then in 2026. It takes seven to nine months just to get there, which means that Musk's hypothetical rocket would have to launch about two years from now in order to hit the deadline.
So, the earliest possible landing date is 2025. That's a Herculean task. Some former SpaceX guys claim they can launch a lander in 2024, but that would also be the first time they even launch a rocket. It's not happening. Realistically, someone would have to test getting stuff back before tossing actual human beings out there, unless they could find crew that would accept a high probability of a one-way trip in return for the notoriety. They would also have to train them.
Conclusion: Musk owns a company and has absolutely no clue how it does what it does. He thinks he's Kennedy, and can just will this into existence on his timetable, simply because someone else claims they can beat him to it. The Moon was doable in the timeframe provided because we already had the rocket designed, took some shortcuts in the testing process to manage the inevitable development problems and weren't bound by the same launch window problem. This just isn't.