I believe developers saw the the vision of Bitcoin and try to explore from the vision by introducing and making their own coin but they lost focus because they only have one goal in mind which is making money, forgetting the most vital ingredients in developing an asset. They forget that they are certain steps and strategies to undergo before accomplishing a good assets or goal.
Some of the reasons why I think some developers fail is because:
1. Lack of funding both the starting aspect and the launching aspect (lack of money to continue)
2. Failure in out righting frauds
3. Failure to evolve especially when the coin initially start bomming
Most developers have only one vision which is making money that is why many coins doesn't grow and they failed because they didn't see the vision ahead.
I honestly think that the dimension that a lot of people neglect is marketability.
Sure, you can come up with the best solution, with the most amount of funding by institutional VCs, etc., but if you can't market your coin/ecosystem to the layman, then you're probably not going to attract a lot of long term users.
This is why DeFi protocols like $FTM and $SOL are so successful - they appeal to the retail with cheap fees and fast transactions.