why is the BSV dev ecosystem empty

You mean you can't find information? Agora.icu is a great place to start. Also bsvdevs.com gives you plenty to start from if you are a developer yourself.

or at least docs

like i can’t even find a lib to form a TX. https://github.com/moneybutton/bsv has ~1000 words of docs

MoneyButton has some doc on that library and a few videos

they didn’t provide the level of depth i need unfortunately

Data pay or data button libs will do it for you. You can also use electrumsv and just attach a file

i don’t want a button tho i want to build TX’s from scratch backend. i guess, what’s the equiv to the web3 lib?

Maybe this can help you out https://libitx.github.io/proxypay/

this is actually very very helpful https://github.com/libitx/proxypay/blob/master/docs/index.html