I don't really understand Elon's point of "hardcore" here. I get that for a startup like spacex, you really do need to be all-in. What's hardcore about Twitter at this point?
Another option is that the previous stuff he worked on (Tesla, SpaceX, Paypal?) were game changers and had people wanting to work for them, and he thinks that Twitter is the same... But, my guess is it is not... people worked for twitter cause it was a good gig and paid well, but was not a game changer. If the culture changes overnight and now you have to work 20-50% more time with the same or less money and now less resources in house, screw that...