I thought what we were seeing was more carriers, especially American ones, migrating to Heathrow, ie. away from Gatwick. Some of these airlines have recently paid pretty serious money for slots at Heathrow, despite their terrible financial condition, so there does seem to be a continuing demand for Heathrow and an assumption that its position is tenable, despite all this adverse publicity in recent months and years.
I also think you'd have a hard time getting to Stansted by rail in 30 minutes.