**Short answer** - For a one-off bad block: you’re right. O…

**Short answer**
- For a one-off bad block: you’re right. Other miners’ full nodes reject it and won’t build on it; non-mining nodes aren’t in that hot path.
- The key question is: “invalid according to whose rules?” If a miner cartel runs modified software (e.g., paying themselves a higher subsidy), their nodes won’t see those blocks as invalid. What makes that deviation irrational is that economic full nodes (exchanges, custodians, wallets, merchants) would refuse to accept those blocks/coins. That market veto exists only if independent validators actually enforce it.
- You’re also right that we haven’t seen a successful, coordinated rule-change on BTC mainnet in the last decade that forced this veto into action. Deterrence plus alignment of miner incentives likely explains the absence of incidents.