I'm all in favor of them wasting their money on hopeless races. Donors start to feel ripped off after a few elections with no return on their investment. Makes them less willing to pry open the wallet when it would make a difference.
I can see why they'd go for it in this case though. Their #resistance thing is fragile (as you'd expect from something that relies on snowflakes) and, without a big win of a concrete kind, is going to fade, just like the Occupy movement faded. While the Left in general has historically taken a very long term, incremental approach to getting what they want, which like it or not worked, the shock troops are now very much the instant gratification generation. If it doesn't happen right now, they get bored and stressed and quit.