Exam JN0-360 topic 1 question 96 discussion

-- Exhibit --
user@R1> show
interfaces {
ge-1/1/0 {
unit 0 {
family inet {
address 10.100.1.1/30;
}
family iso;
}
}
lo0 {
unit 0 {
family inet {
address 10.100.10.1/32;
}
family iso {
address 49.1001.0010.0100.00;
}
}
}
}
protocols {
isis {
level 1 disable;
interface ge-1/1/0.0 {
level 2 disable;
}
interface lo0.0;
}
}
user@R2> show
interfaces {
ge-1/1/0 {
unit 0 {
family inet {
address 10.100.1.2/30;
}
family iso {
mtu 1496;
}
}
}
lo0 {
unit 0 {
family inet {
address 10.100.10.2/32;
}
family iso {
address 49.1002.0010.0200.00;
}
}
}
}
protocols {
isis {
interface ge-1/1/0.0 {
level 2 disable;
}
interface lo0.0;
}
}
-- Exhibit --
Click the Exhibit button.
Referring to the exhibit, R1 and R2 are directly connected using interface ge-1/1/0.
What is the reason the IS-IS adjacency fails?