They didn't make 50%, that isn't how 1x liquid prefs work. They take back their principle first so +$225m, then from there they split the portion that they own, say 22.5% of 1.3 is +$293m. Total around $523m or 130% gain. For an investment fund at this stage, that is well within normal gains.
That's only true if the investment was participating preferred equity (sometimes known as "double-dipping"); if it was convertible preferred equity then it's an either/or scenario (they choose between getting their liquidation preference, or converting to common equity and getting their pro rata %). Insight used to be big on participating prefered so I wouldn't be surprised if you're right, but things may have changed..
