In what way were Brexit or Trump "forced underground"? Trump got millions of dollars worth of free advertising from the second he announced he was running because the media could not stop covering him. CNN, MSNBC, and Fox aired 30 minutes of an empty podium for him!
And Brexit was constantly in the media in the UK. There was no "underground" at all. The BBC were almost a full-on propaganda arm with their fawning over Farage and terror that any even slight non-worship of the Tories would be reflected in yet more license fee beatings by ukgov.