GPIO15 must be low at start up both for normal operation or for serial uploading. I could understand it if some leakage current from strobe was causing that not to be the case as the pull down resistor on the NodeMCU board is 12K which is a bit high to give a solid pull down and that could be cured by putting an external additional pull down on that line e.g. 2k2. I would do that anyway to make sure it is starting up correctly.
However, if that was the case it would also be preventing normal operation as well as uploading.
You do need to disconnect busy for uploading in that wiring scheme as otherwise the RX pin won't be able to get the serial data from the usb serial interface. You could avoid that issue by swapping GPIO3 (RXD) for one of the data lines in the assignment.
If you are getting garbled output the first thing to check is that the data lines do correspond exactly.