Why doesn't GC collect objects without references?

Question

public static void main(String[] args) {
    try {
        Path file = Paths.get("file.jar"); // 100mb file
        for (int i = 0; i < 10; i++) {
            byte[] toCollect = Files.readAllBytes(file);
            toCollect = null;
        }

        System.gc();
    } catch (Exception e) {
        e.printStackTrace();
    }

    new Thread(() - > {
        try {
            Thread.sleep(100000000L);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }).start();
}

After executing this code the program uses 1GB of RAM, why?
This code reads bytes from a file using the JAVA API and puts them into an array, then assigns null to that array.