Fiat is very important and it is better for the normal lives i would like to say that bitcoin is very good and profitable for investment rather than investing in fiat people were investing in Dollars and pounds but now the trend is changed and people happily invest in it. So it shows importance of fiat that now people pay fiat for investing in crypto.
The investors not only from the dollars and pound but also the gold investors coming to invest in Bitcoin. These are currently smaller in amount which will be increased much more when any ETF will be approved. The it is possible that all of the stock exchange investors invest in Bitcoin some amount of their money.