Understanding the relationships between cryptocurrencies is important for making informed investment decisions in this financial market. Our study utilises Bayesian networks to examine the causal interrelationships among six major cryptocurrencies: Bitcoin, Binance Coin, Ethereum, Litecoin, Ripple, and Tether. Beyond understanding the connectedness, we also investigate whether these relationships evolve over time. This understanding is crucial for developing profitable investment strategies and forecasting methods. Therefore, we introduce an approach to investigate the dynamic nature of these relationships. Our observations reveal that Tether, a stablecoin, behaves distinctly compared to mining-based cryptocurrencies and stands isolated from the others. Furthermore, our findings indicate that Bitcoin and Ethereum significantly influence the price fluctuations of the other coins, except for Tether. This highlights their key roles in the cryptocurrency ecosystem. Additionally, we conduct diagnostic analyses on constructed Bayesian networks, emphasising that cryptocurrencies generally follow the same market direction as extra evidence for interconnectedness. Moreover, our approach reveals the dynamic and evolving nature of these relationships over time, offering insights into the ever-changing dynamics of the cryptocurrency market.

Despite advances in artificial intelligence-enhanced trading methods, developing a profitable automated trading system remains challenging in the rapidly evolving cryptocurrency market. This study aims to address these challenges by developing a reinforcement learning-based automated trading system for five popular altcoins~(cryptocurrencies other than Bitcoin): Binance Coin, Ethereum, Litecoin, Ripple, and Tether. To this end, we present CausalReinforceNet, a framework framed as a decision support system. Designed as the foundational architecture of the trading system, the CausalReinforceNet framework enhances the capabilities of the reinforcement learning agent through causal analysis. Within this framework, we use Bayesian networks in the feature engineering process to identify the most relevant features with causal relationships that influence cryptocurrency price movements. Additionally, we incorporate probabilistic price direction signals from dynamic Bayesian networks to enhance our reinforcement learning agent's decision-making. Due to the high volatility of the cryptocurrency market, we design our framework to adopt a conservative approach that limits sell and buy position sizes to manage risk. We develop two agents using the CausalReinforceNet framework, each based on distinct reinforcement learning algorithms. The results indicate that our framework substantially surpasses the Buy-and-Hold benchmark strategy in profitability. Additionally, both agents generated notable returns on investment for Binance Coin and Ethereum.