The biggest mistakes developers make that leads to bad ending for many projects are
1. Huge Discounts
Many new projects are still making this mistake over and over again, huge discounts like 50% is insane and it always bother me how the hell the early buyers won't end up dumping since they have already see big profits.
2. Lack Of Solid Products and Ideas
Lack of working products and real use cases is why many investors are not taking new projects very seriously, no one would want to hold such tokens or coins for long, developers need to start working on how their project's token or coin will be very demanding throughout the globe
3. Bad Exchanges
Imagine new projects that make over millions of dollars in ico or ieo and end up listing on bad exchanges with no enough volume, what do they expect to happen?
Glad you've pointed this out! Additionally, I would like also to emphasize one of the most important blunders that has been plaguing projects for a long time now and it is because
they have poor financial planning! I think this is one of the main reasons why most projects had failed and this is evident when most projects suddenly went inactive even after they have gathered a sufficient amount of funding during their respective ICO's!
I've even heard some projects way back 2018 that went financially unstable because they were not able to diversify their funding source which is
mostly in BTC or ETH or haven't opted to exchange it to fiat and had incurred huge losses when crypto prices fell sharply especially when BTC sinks to less than $4k last December 2018. If only they had a sound financial planning, then we could have seen some promising projects which is still active up to this day!