https://shai-deshe.gitbook.io/parallel-thoughts/proof-of-work/the-qubic-minority-report

TLDR; just because you have >=51% of the blocks in a certain timespan, does NOT mean you control 51% of the hashrate. Due to probability, you can expect anyone with any non-zero hashrate to produce more than 50% of blocks in a timeframe of some length with some probability. If you near 33% of total hashrate, that can be pretty often in practice. According to this report, Qubic never breached 40% of the total hashrate, and hovered around 1/3 of the total hashrate during active mining marathons, which weren’t pepetually on-going. Qubic increased the average actualized hash-rate over its whole operation by ~5%.