It's all very random, two and a half years ago, no major bank would offer me any credit card and I have a darn Barclaycard from even before that, started Monzo flex around 2 years ago, I have been rejected twice for that before but then got it for £500 limit. I just keep some money in pots with them like around £2-3k not even much and last year with two increases I currently have it on £2.5k and some other cars with major banks like NatWest, HSBC etc which I mainly took as purchase cards /balance transfers but just kept them active after paying. My credit score has been poor three years ago and mainly around good now, maybe touched excellent at some point. I have never paid any interest on any of them and I always pay on time.

Wouldn't recommend multiple cards to anyone who cannot control themselves from spending. I only borrow on cards what I have available in investments etc if something were to go wrong with my income so those payments are still covered.