This is a noob question but I have just pulled https://github.com/succinctlabs/rsp/ and try to build it but it fails

$ cargo build
   Compiling rsp v0.1.0 (/Users/clementwalter/Documents/rsp/bin/host)
error: failed to run custom build command for `rsp v0.1.0 (/Users/clementwalter/Documents/rsp/bin/host)`

Caused by:
  process didn't exit successfully: `/Users/clementwalter/Documents/rsp/target/debug/build/rsp-766fbc07d4535559/build-script-build` (exit status: 101)
  --- stdout
  cargo::rerun-if-changed=/Users/clementwalter/Documents/rsp/bin/client-eth/src
  cargo::rerun-if-changed=/Users/clementwalter/Documents/rsp/bin/client-eth/Cargo.toml
  cargo:rerun-if-changed=/Users/clementwalter/Documents/rsp/bin/client-eth/Cargo.lock
  cargo:rerun-if-changed=/Users/clementwalter/Documents/rsp/crates/executor/client
  cargo:rerun-if-changed=/Users/clementwalter/Documents/rsp/crates/mpt
  cargo:rerun-if-changed=/Users/clementwalter/Documents/rsp/crates/primitives
  cargo:rerun-if-changed=/Users/clementwalter/Documents/rsp/crates/storage/witness-db
  cargo:rerun-if-changed=/Users/clementwalter/Documents/rsp/crates/primitives
  cargo:rerun-if-changed=/Users/clementwalter/Documents/rsp/crates/mpt
  cargo:rerun-if-changed=/Users/clementwalter/Documents/rsp/crates/primitives

  --- stderr
  [sp1]  error: package `reth-trie v1.0.6 (https://github.com/sp1-patches/reth?tag=rsp-20240830#260c7ed2)` cannot be built because it requires rustc 1.80 or newer, while the currently active rustc version is 1.75.0-nightly
  [sp1]  Either upgrade to rustc 1.80 or newer, or use
  [sp1]  cargo update [email protected] --precise ver
  [sp1]  where `ver` is the latest version of `reth-trie` supporting rustc 1.75.0-nightly

while I also have

$ rustup show active-toolchain
1.81.0-aarch64-apple-darwin (overridden by '/Users/clementwalter/Documents/rsp/rust-toolchain.toml')

So I don’t understand where this 1.75 version comes from, and why it’s chosen