You could say the interbank market used to work like a clock. Or, more appropriate, like a beating heart (which is actually quasiperiodic, unlike a clock). The last 8 months look like cardiac arrest.

The reference levels here are the ECB's deposit and marginal rates of 0.25% and 1.75%

The ECB pays 0.25% overnight for excess bank reserves, so this is a lower bound for EONIA as banks can always park their excess cash at the ECB instead of lending to each other. The baseline EONIA level seems to be 0.32%, or 7 basis points (hundredths of a percent) above the ECB's deposit rate.

The ECB charges 1.75% overnight for collateralised lending to make up for reserve shortfalls, so this is an upper bound for EONIA as banks can always borrow from the ECB at the marginal rate if the other banks charge them more for overnight lencing. The EONIA appears to have reached 1.30% in Early January, which is scarily close to 1.75%

But most importantly, EONIA used to have single-day spikes but now rates stay elevated for weeks on end.

This actually bears looking at a longer data series.

Keynesianism is intellectually hard, as evidenced by the inability of many trained economists to get it - Paul Krugman