Here is an example of a multi-bet strategy that improves your odds over a single bet strategy for a fixed bankroll.

Strategy 1: Bet 3 BTC, p = 0.7425         - get 4 BTC with p = 0.7425
Strategy 2: Bet 1 BTC, p = 0.495,
                if lose bet 2 BTC, p = 0.495. - get 4 BTC with p = 0.744975

Strategy 2 has better odds, by p = 0.002475 or 0.3%.  Strategy 2 is martingale starting bet of 1, exit of 4 or bust.

This is explained by the fact that Strategy 2 doesn't bet 3 BTC unless the first bet loses whereas Strategy 1 bets 3 BTC.  Your expected losses are proportional to the total amount bet.  The average amount bet with Strategy 2 is 2 BTC.

This is an example of the principal that: The less you bet the less you lose.

It is essential for each strategy that you stop betting.  The amount you lose grows with each bet.