It was a reaction to regulatory over-reach by unelected officials on the continent, which even those officials acknowledged at the time: https://www.politico.eu/article/jean-claude-juncker-says-eu-...
Yet I don't think that anybody can argue that it was handled well. It was handled abysmally poorly.
- The regulatory burden on individuals and small businesses has increased quite dramatically since Brexit. New customs declarations, VAT rules, compliance checks, etc.
- Transit of goods to and from EU states is now many times more difficult than it was, and a lot of European firms simply don't want to ship to the UK any longer.
- Temporary skilled immigration from places like Poland and Romania has been replaced by permanent and largely unskilled immigration from places like Pakistan. En masse. Much to the consternation of Brexit voters, who have, for the most part, simply become anti-status-quo voters.
The impression I get is that the UK political establishment reclaimed some control over its laws, regulations, and borders -- and proceeded to spite the populace with them. Maybe they wanted revenge for being forced into a Brexit they didn't want to go through with. "We'll give it to 'em, good and hard."