Why is Nara Lokesh rushing to Tirupati

It was to be a simple bypoll where sympathy wave holds the sway.

Yes. We are talking of Tirupati bypoll, necessitated by the death of sitting TDP MLA Venkata Ramana. 
Though the chief Opposition YSRCP has decided against fielding a candidate as a mark of respect for the late MLA, the Congress has decided to give a fight. But, more than the Congress, it is the internecine squabbles in the TDP and the craving for control over money bags that is marring the TDP show. With key leaders turning lukewarm, the party campaign is proving to be a non-starter for the TDP.
TDP wants not just to win, but handsomely too as even a marginally better Congress performance could be interpreted as a waning of TDP popularity.  To bring all the partymen together and make them work for the party, CM Chandrababu Naidu's son Nara Lokesh is coming to Tirupati on Friday. He will hold a key meeting at Hotel Uday International.  
The TDP wants to better its performance over last time to show that there is no waning of popularity, while the Congress wants to leverage on the anger of the DWCRA women and improve its performance.