From my understanding, you are asking why there is no mention of an asymmetric algorithm in the cipher suite “TLS_AES_128_CCM_SHA256”, and the certificate is not relevant to the question.
This is because TLS1.3 negotiates it differently than it used to be, as detailed in RFC8446 Section 4.1.1 - Cryptographic Negotiation:
In TLS, the cryptographic negotiation proceeds by the client offering
the following four sets of options in its ClientHello:
A list of cipher suites which indicates the AEAD algorithm/HKDF
hash pairs which the client supports.
A "supported_groups" (Section 4.2.7) extension which indicates the
(EC)DHE groups which the client supports and a "key_share"
(Section 4.2.8) extension which contains (EC)DHE shares for some
or all of these groups.
A "signature_algorithms" (Section 4.2.3) extension which indicates
the signature algorithms which the client can accept. A
"signature_algorithms_cert" extension (Section 4.2.3) may also be
added to indicate certificate-specific signature algorithms.
A "pre_shared_key" (Section 4.2.11) extension which contains a
list of symmetric key identities known to the client and a
"psk_key_exchange_modes" (Section 4.2.9) extension which indicates
the key exchange modes that may be used with PSKs.
Note that RFC8442 regarding TLS1.2 also quotes your cipher suite explaining it is used to "support equivalent functionality in TLS 1.3".