There are many causative verbs but some of them are followed by object + infinitives (to + base form of infinitive form of verb) while some are followed by object + bare infinitives.
- I let my students talk most of the time.
- I will have my assistant prepare me dinner.
- I will make her understand my point.
The reason why let, have and make are called true causative verbs is because they are the ones followed by object + bare infinitive/base form of verb.
Please note that have can be used in passive voice, and its form is have + object + past participle.
- I will have my dinner prepared soon.
- She is having her clothes ironed.
Other causative verbs cause, allow, help, enable, force, require, persuade, etc. are followed by object + infinitive (to + bare infinitive/base form of verb).
- The doctor allowed his patient to go home.
- The court allowed him to post bail.
- My brother helped me (to) cook the turkey.
- My tablet enables me to work wherever I am.
- My boss forced me to work until midnight.
- The government requires all the citizens to pay income taxes.
- A politician persuaded the people to vote for him.
Help can use both forms with no difference in meaning.