Musk is 'rich' but he's not that rich. He needed massive investment to get both his major companies off the ground. Without massive investment he wouldn't have gotten anywhere with cars or with rockets. If one fails then investment in new ventures dry up. When a tech leading guy's ventures start failing badly then people stop believing and stop investing. So Tesla failing would be a huge blow to every future venture he has.
In terms of electric cars not being the be all and end all, there are some seriously incorrect statements being made.
First of all electricity produced in power stations is drastically more efficient than energy produced in each car. Second, even if you 'just moved the pollution out of cities'... you'd save millions of lives while improving the health and quality of life of billions of people. City pollution has an effect on everyone's health and reduces lifespan anywhere between a small amount to everyone and actual cancers and lung conditions causing the deaths of many.
Electric cars means cleaner, quieter, healthier cities, that is monumental on it's own.
Third, petrol cars idle a lot, there is a huge amount of waste particularly in cities and lots of additional traffic in cities with huge awkward fuel trucks all of which can be eliminated. electric cars are drastically more efficient and less pollution producing in cities.
Electric in in the trucking industry will also be huge. Lack of noise from electric delivery trucks combined with self driving so there are less issues scheduling deliveries means we can more easily shift most trucks to delivering at night where there is less traffic.
For instance right now you have lets say a 30 hour drive from somewhere in europe to London, as they have to stop every 8 hours then they can't waste time and if they arrive in London at midday for rush hour that's when they arrive. With self driving trucks, no large gaps between driving stints suddenly the trip takes half as long and you can have them wait 5 hours outside London and all come in after rush hours with no huge noise to wake everyone up. IT will alleviate traffic massively. Having fleets of loud petrol trucks rolling in through the night wouldn't be possible, electric will make that possible. That means for the millions of petrol cars that already exist, less traffic, less idling, less pollution.
Electric vehicles will have a monumental effect on our lives, traffic in cities and pollution where the majority of people actually live allowing us far far higher air quality in most cities in the world.
Lastly on hydrogen, meh, there isn't much stopping us getting to the point where we have hydrogen capturing stations around the country sitting next to nuclear or massive wind or solar farms. Produce the hydrogen when you have excess energy and use hydrogen power cells as storage. THis can be split between both hydrogen cells for cars and simply using hydrogen cells as a battery. When the grid needs more juice you can use the hydrogen cells to top up the grid.
Electric cars alone is huge, combined with self driving will have an even bigger effect.