Low market cap of the whole market or only cap of the only coin you've ment installing your qestion? It's two big differencies like Russians used to say...
The low market cap of the whole crypto market is a bad thing, it means investors withdraw their investments out of cryptoworld and othet men who were intended to deposit looking at such things going on think it's not right moment to invest. So the cap begins to get lower and lower and BTC with other Alts drop down.
The low market cap (LMC) of a any coin can help this coin but it doesn't mean LMC will do it in any case.