What happened

Easy come, easy go.

Following three days of steadily rising stock prices reinforced by a positive analyst report Wednesday, shares of EV truck-maker Rivian Automotive (RIVN -2.94%) shifted back into reverse on Friday morning -- down by 3.3% as of noon ET. Fellow electric truck-making start-ups Canoo (GOEV -3.11%) and Workhorse Group (WKHS -3.70%) weren't faring any better, down 3.6% and 6.3%, respectively.

Why is all this happening? I blame Tesla (TSLA 3.46%) -- and its Cybertruck.

So what

To great fanfare last weekend, Tesla rolled the first production model of its Cybertruck off the assembly line.

Mass production won't start until next year, but once it does, Elon Musk is promising to rapidly ramp up to produce 375,000 Cybertrucks per year -- and even then, it may take several years to satisfy all the demand for Tesla's electric pickup. On the latest earnings call, the Tesla CEO described pre-orders for Cybertruck as "so far off the hook, you can't even see the hook," with one online tracker clocking pre-orders at 1.9 million units.    

Simply put, when combined with the much larger Tesla Semi (already in production, and ramping toward 50,000 units next year) once the Cybertruck reaches mass production levels, it's going to suck a lot of oxygen out of the EV room, and make it a lot harder for other electric truck manufacturers to compete.  

Now what

Granted, given that Tesla is only asking for a $100 refundable fee to place a pre-order, its pre-order numbers are more of a marketing gimmick than an assurance of eventual sales. But even so, Cybertruck's popularity feels very real at this point.

Meanwhile, Rivian seems to be facing uncertain demand for its R1T electric pickup, even as it struggles to match a $6.8 billion-a-year cash burn rate against cash reserves that have dwindled to just $11.2 billion -- enough to keep it going for less than two years. Workhorse was down to just $79 million cash at last report -- and it's burning $115 million a year. On Thursday night, the company filed a plan to sell up to $200 million worth of common stock, preferred stock, warrants, debt securities, "and guarantees thereof," in a last-ditch effort to stay solvent. It's uncertain whether there will be any takers, however, or whether -- after all the dilution implied by the offerings -- there will be much value left for the holders of the shares Workhorse has already sold. And Canoo -- with even less cash and a faster burn rate than Workhorse -- has already conducted two "PIPE" transactions to raise cash in just the last month.    

All in all, things are looking pretty bleak for any electric truck hopefuls that are not named Tesla. I don't blame investors for feeling less than optimistic about them.