They were stuck for 10 minutes and needed to be directed from the outside. It's maybe not that long, but they struggled with figuring it out. Source (in Norwegian, this happened in Oslo): https://www.vg.no/nyheter/i/3pkoP9/busser-fast-paa-alexander-kiellands-plass-i-oslo

there are probably cars there facing the bottom bus, no? it's the enter lane, not an exit lane

It is, but none of the four bus drivers have all of the information. You will also need two or three cops or at least guys in fluorescent vests to physically block traffic from entering the circle and or bitch-slap selfish asshats as necessary until the Gordian knot of buses is untied, otherwise said selfish asshats will try to barge into the intersection the second the first bus moves and start everything all over again.

Also, fewer cars will help.