It is stack overflow. To compile C++23 solutions, Codeforces uses the following command: g++ -Wall -Wextra -Wconversion -static -DONLINE_JUDGE -Wl,--stack=268435456 -O2 -std=c++23 program.cpp -lstdc++exp -- it gives 256 MiB for stack. But for this program it is not enough. 450 MiB fixes the issue: 291681903. I'd say that on a 32-bit architecture, the pointer consumes less memory, which is why there is enough stack.

#include <bits/stdc++.h>
using namespace std;
using ll=long long;

ll node=2;vector<ll> tree[1];

mt19937 mt;
void usearray(char*c,int len){
    for(int i=0;i<len;++i)c[i]=mt();
     for(int i=len-1;i>=0;--i)c[i]^=c[i+1];
    volatile int res=c[0];
}

ll dfs(ll node, vector<ll> tree[]){
    if(!node)return 0;
     char x[64<<20];usearray(x,64<<20);
int sv;
cout << "Stack Pointer: " << &sv << endl;
vector<ll> v;
dfs(node-1,tree);

return 0;
}

int main(){
 int baseVariable;
 cout << "Stack Pointer0: " << &baseVariable << endl;
 dfs(node,tree);
 cout<<sizeof(vector<ll>)<< ' '<<sizeof(map<ll, ll>)<<' '<<
  sizeof( set<ll, greater<ll>>);
}

It seems G++ 13.2 and 14.2 may preallocate the stack, for the above program, apparently the stack usage should be 128MB (2 calls of dfs, each results 64MB allocation), which conforms G++ 7.3 behavior. But with 13.2 and 14.2, the memory usage is 192MB, which seems it allocates when entering a dfs regardless if the variables are used or not.

Also the size of vector<ll> map<ll, ll> set<ll, greater<ll>> gets doubled in the 64-bit version to 24, 48, 48. Suppose the above preallocation is true, then each call of dfs results 24+48+48+100ish(function call and parameter)=220B, when multiplied 1e6, it's close to 256MB. If add some misc things, that could be an overflow.