Look closer, it was clogged. They run fine all day long and by the millions with that part on there OR.............
..............you have only bought a small amount of time until it does it again. A marginal pump can start working again with any improvement in reduction of suction needed to prime it but will shortly usually start doing it again WITHOUT the round filter on it. All it needs is a bit more wear.
That filter circle cleans off perfectly with WATER, ethanol borne fuel trash is what stops them up.