Climate activists can lobby in person when available, taking time away from other things. Oil companies can hire armies of lobbyists - some of whom masquerading as “concerned citizens” - to overwhelm public hearings, buy out media companies to manipulate public opinion and engage in astroturfing campaigns, and directly sway politicians with legal bribery (deliberately being vague about the purpose of “gifts” to maintain the benefit of the doubt about there being any quid pro quo involved).
Lobbying effectively requires resources - namely capital - which oil companies have in abundance and climate activists do not. To suggest that climate activists should simply fight on their terms is ignorant at best and malicious at worst.