Roads are much easier to interconnect than rails because road vehicles can make much sharper turns and handle steeper grades.

Point to point navigation has high utility and is difficult to acheive with rail.

Minimum viable roads are actually quite inexpensive: clear large vegetation from the path and there's a usable road. You can incrementally improve with path markers, grading, gravel, pavement, etc. Minimum viable rail is a much higher standard, which needs grading, railbed preparation, laying the rail, signalling and operations.