That's hardly correct. In most countries there're at least 3-4 tiers of ref categories you have to go through, refereeing youths and lower leagues, taking abuse from parents and the semi-professional mechanic-footballers etc. Once you go through that (it takes at least a year or two even in a small footballing country, let alone a big one), you get to ref the higher domestic leagues, where, if you prove yourself, after some time (again, at least a year or two) you'll get promoted to UEFA category, meaning you'll get to ref EL/CL games.
It's way easier than becoming a professional footballer, but it's also way less rewarding. For sure there've been corrupt refs over the years, possibly even bribed by FIFA / UEFA (although FIFA sounds more likely, they're the dirtier org between the two imo, most of UEFAs corruption problems are linked with FIFA), but I don't think any of the corrupt refs started out in a U12 futsal game with the ambition of being dirty on the big stage, it's a very long con