The visual representation of the drawing is defined in the KML file.
Every shape in the KML file has a style definition (e.g.):
<styleUrl>#Style8-multi_geometry-4-map</styleUrl>
Which is mapped to a StyleMap (containing multiple styles) or Style. The style defines what is drawn on the map, here is an example which draws a filled polygon with a border:
<Style id='Style8-polygon-3'>
<LabelStyle>
<scale>0.0</scale>
</LabelStyle>
<LineStyle>
<color>ff666666</color>
<width>1</width>
</LineStyle>
<PolyStyle>
<color>7f0000ff</color>
</PolyStyle>
<BalloonStyle>
<text>$[description]</text>
</BalloonStyle>
</Style>
If styles are missing for the shapes in your KML file you might see nothing on the map.
Regarding the loading time, for 3MB 2 minutes seem normal to me. Under the hood is an XML parser which is not the fastest. You could look at converting the KML to GeoJSON. Tools for conversion can be found online, styling is not applied after conversion, that has to be set manually. Minify the GeoJSON to keep the filesize small.
GeoJsonLayer layer = new GeoJsonLayer(map, R.raw.crime, getContext());
layer.getDefaultPolygonStyle().setFillColor(getResources().getColor(R.color.accent));
layer.getDefaultPolygonStyle().setStrokeColor(getResources().getColor(R.color.accent));
layer.getDefaultPolygonStyle().setStrokeWidth(1);
layer.addLayerToMap();