It's not the most frequent verbs. It's the verbs with most forms. For frequency see:
500 most frequent dhatus in Rāmāyaṇa
kṛ (2. P.) 2045 occurrences
dṛś (6. P.) 1830 occurrences
gam (6. P.) 1610 occurrences
vac (2. P.) 1402 occurrences
bhū (1. Ā.) 1320 occurrences
brū (2. Ā.) 1193 occurrences
śru (4. P.) 1064 occurrences
as (2. P.) 1055 occurrences
han (6. P.) 725 occurrences
sthā (1. Ā.) 556 occurrences
āgam (6. P.) 457 occurrences
prāp (1. P.) 427 occurrences
dā (1. Ā.) 417 occurrences
praviś (4. P.) 334 occurrences
iṣ (1. P.) 328 occurrences
arh (1. Ā.) 307 occurrences
pat (1. Ā.) 305 occurrences
grah (6. P.) 297 occurrences
nihan (2. Ā.) 290 occurrences
paś (4. Ā.) 272 occurrences
yā (2. Ā.) 253 occurrences
krudh (4. Ā.) 252 occurrences
yuj (2. Ā.) 248 occurrences
vas (2. P.) 245 occurrences
jñā (4. Ā.) 219 occurrences
muc (6. Ā.) 214 occurrences
man (8. P.) 207 occurrences
tyaj (1. Ā.) 206 occurrences
hṛṣ (1. Ā.) 194 occurrences
dīp (4. P.) 183 occurrences
jan (4. P.) 179 occurrences
hṛ (2. P.) 178 occurrences
hā (1. P.) 166 occurrences
vṛ (9. P.) 165 occurrences
vid (6. Ā.) 164 occurrences
vṛt (1. P.) 162 occurrences
prī (4. P.) 157 occurrences
nipat (1. Ā.) 156 occurrences
śak (4. P.) 154 occurrences
jīv (1. Ā.) 150 occurrences
ādā (4. Ā.) 147 occurrences
āsāday (10. P.) 147 occurrences
sampad (4. P.) 145 occurrences
rakṣ (1. Ā.) 140 occurrences
bhid (6. P.) 139 occurrences
labh (1. P.) 137 occurrences
prativac (3. Ā.) 136 occurrences
utthā (1. Ā.) 136 occurrences
pūjay (10. Ā.) 135 occurrences
car (1. Ā.) 133 occurrences