There are three stocks I’m aware of (CHPT, EVGO, LCID), which crashed right after they reported that workers and “big stake” investors are allowed to purchase a big amount of common stocks for a lower price. I’m wondering why this happens. Isn't it supposed to increase the stock price?
The 15% discount is standard for an ESPP, completely within regulations, and ESPPs are done by most US tech companies - which should also show this behaviour if there was any connection.
The behaviour you are seeing is probably just coincidence on volatile stocks. There might have just been other things that actually moved the stock:
CHPT announced a 20-year ESPP program in February 2021 in a stockholders meeting. In the same meeting, they also announced the merger with a spac, which means a major financial restructuring. You can untangle how much of the stock movement belonged to the ESPP and how much movement was due to now being a publicly traded company at the NYSE from March, 1st (which was the reason for the merger).
LCID announced its program in July 2021. There doesn't seem to have been big movements during July, but maybe you mean a different date (but if you do, this still shows that an ESPP for LCID doesn't cause a crash in general). In any case, LCID moved from $10 to $38 in 2021, with news-driven intermediate spikes to above $50 in February and November. This is neither a crash, nor would I assume (without a more detailed analysis) that, if there were, it would be caused by the ESPP and not some other news, which there were plenty of.
EVgo dropped from its IPO in 2021 from $15 to below $3 today. I don't know which ESPP you are referring to, but given the general trend, there was probably something else impacting the stock. But in general: an ESPP for 200-ish employees with "costs" (if you can call them that) of maybe $1 million a year (which is 0.04% of the $2.6 billion IPO valuation) shouldn't be expected to cause a crash. Daily random stock movements oftentimes are worth more than this.